Attachment 360265 Details for Bug 193879 – Patch

[patch] Patch

bug-193879-20190126210836.patch (text/plain), 70.69 KB, created by Simon Fraser (smfr) on 2019-01-26 21:08:38 PST

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Creator: Simon Fraser (smfr)

Created: 2019-01-26 21:08:38 PST

Size: 70.69 KB

patch

obsolete

>Subversion Revision: 240551
>diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
>index aaa113994d607050cafb0e90b26bcb69e95e3225..a1c7f3e6fed53da177a2c03998ce23e7e1afa67f 100644
>--- a/Source/WebCore/ChangeLog
>+++ b/Source/WebCore/ChangeLog
>@@ -1,3 +1,47 @@
>+2019-01-26  Simon Fraser  <simon.fraser@apple.com>
>+
>+        Have composited RenderIFrame layers make FrameHosting scrolling tree nodes to parent the iframe's scrolling node
>+        https://bugs.webkit.org/show_bug.cgi?id=193879
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        Currently we parent iframe scrolling tree nodes by finding the closest ancestor layer with a scrolling tree node.
>+        This results in scrolling tree nodes being connected across iframe boundaries in some arbitrary ancestor. This
>+        makes updating scrolling tree geometry very error-prone, since changes in the parent document will need to trigger
>+        updates of the scrolling tree node in an iframe.
>+        
>+        To address this, I already added a new "FrameHosting" scrolling node type. This patch actually instantiates these
>+        nodes, which are owned by the RenderIFrame's composited layer. Connecting across frame boundaries is theforefore
>+        simply a case of getting the FrameHosting node from the ownerElement's renderer; this is very similar to how we
>+        connect GraphicsLayers together.
>+        
>+        RenderLayerBacking gains another scrolling role for FrameHosting and ScrollingNodeID.
>+
>+        Tested by existing tests.
>+
>+        * page/FrameView.h:
>+        * rendering/RenderLayer.cpp:
>+        (WebCore::outputPaintOrderTreeRecursive):
>+        * rendering/RenderLayerBacking.cpp:
>+        (WebCore::RenderLayerBacking::updateConfiguration):
>+        (WebCore::RenderLayerBacking::detachFromScrollingCoordinator):
>+        * rendering/RenderLayerCompositor.cpp:
>+        (WebCore::frameContentsRenderView):
>+        (WebCore::RenderLayerCompositor::frameContentsCompositor):
>+        (WebCore::RenderLayerCompositor::parentFrameContentLayers):
>+        (WebCore::RenderLayerCompositor::isLayerForIFrameWithScrollCoordinatedContents const):
>+        (WebCore::RenderLayerCompositor::detachRootLayer):
>+        (WebCore::RenderLayerCompositor::updateScrollCoordinatedStatus):
>+        (WebCore::RenderLayerCompositor::removeFromScrollCoordinatedLayers):
>+        (WebCore::scrollCoordinatedAncestorInParentOfFrame):
>+        (WebCore::RenderLayerCompositor::reattachSubframeScrollLayers):
>+        (WebCore::RenderLayerCompositor::attachScrollingNode):
>+        (WebCore::RenderLayerCompositor::updateScrollCoordinationForThisFrame):
>+        (WebCore::RenderLayerCompositor::updateScrollCoordinatedLayer):
>+        * rendering/RenderLayerCompositor.h:
>+        * testing/Internals.cpp:
>+        (WebCore::Internals::scrollingStateTreeAsText const):
>+
> 2019-01-26  Simon Fraser  <simon.fraser@apple.com>
> 
>         Allow scrolling tree nodes to exist in a detached state
>diff --git a/Source/WebKit/ChangeLog b/Source/WebKit/ChangeLog
>index 03a1013b6dcc3be10fd251b1ca4d7d97914c3e1d..19b77a8d0cdc52aa50ac5f70a44773613d0702a8 100644
>--- a/Source/WebKit/ChangeLog
>+++ b/Source/WebKit/ChangeLog
>@@ -1,3 +1,15 @@
>+2019-01-26  Simon Fraser  <simon.fraser@apple.com>
>+
>+        Have composited RenderIFrame layers make FrameHosting scrolling tree nodes to parent the iframe's scrolling node
>+        https://bugs.webkit.org/show_bug.cgi?id=193879
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        Need a specialization of dump() for ScrollingStateFrameHostingNode to avoid infinite recursion.
>+
>+        * Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp:
>+        (WebKit::dump):
>+
> 2019-01-26  Simon Fraser  <simon.fraser@apple.com>
> 
>         Allow scrolling tree nodes to exist in a detached state
>diff --git a/Source/WebCore/page/FrameView.h b/Source/WebCore/page/FrameView.h
>index 1b2fe100b5c7e5e9a41bd1bed18b101978ef6950..6a97102976af4d6693ad100cf51ba1f28fd82bdf 100644
>--- a/Source/WebCore/page/FrameView.h
>+++ b/Source/WebCore/page/FrameView.h
>@@ -152,10 +152,9 @@ public:
> 
>     WEBCORE_EXPORT TiledBacking* tiledBacking() const final;
> 
>-    // In the future when any ScrollableArea can have a node in th ScrollingTree, this should
>-    // become a virtual function on ScrollableArea.
>     uint64_t scrollLayerID() const override;
>     ScrollableArea* scrollableAreaForScrollLayerID(uint64_t) const;
>+    bool usesAsyncScrolling() const final;
> 
>     WEBCORE_EXPORT void enterCompositingMode();
>     WEBCORE_EXPORT bool isEnclosedInCompositingLayer() const;
>@@ -746,7 +745,6 @@ private:
> #endif
> 
>     bool usesCompositedScrolling() const final;
>-    bool usesAsyncScrolling() const final;
>     bool usesMockScrollAnimator() const final;
>     void logMockScrollAnimatorMessage(const String&) const final;
> 
>diff --git a/Source/WebCore/rendering/RenderLayer.cpp b/Source/WebCore/rendering/RenderLayer.cpp
>index 2d275fb5aad48ac83ab24814dd03a2471c2e459f..8c4d7f1ea565418098c62474fa5668dcf49d627d 100644
>--- a/Source/WebCore/rendering/RenderLayer.cpp
>+++ b/Source/WebCore/rendering/RenderLayer.cpp
>@@ -6690,8 +6690,38 @@ static void outputPaintOrderTreeRecursive(TextStream& stream, const WebCore::Ren
>     auto layerRect = layer.rect();
> 
>     stream << &layer << " " << layerRect;
>-    if (layer.isComposited())
>-        stream << " (layerID " << layer.backing()->graphicsLayer()->primaryLayerID() << ")";
>+    if (layer.isComposited()) {
>+        auto& backing = *layer.backing();
>+        stream << " (layerID " << backing.graphicsLayer()->primaryLayerID() << ")";
>+
>+        auto scrollingNodeID = backing.scrollingNodeIDForRole(WebCore::ScrollCoordinationRole::Scrolling);
>+        auto frameHostingNodeID = backing.scrollingNodeIDForRole(WebCore::ScrollCoordinationRole::FrameHosting);
>+        auto viewportConstrainedNodeID = backing.scrollingNodeIDForRole(WebCore::ScrollCoordinationRole::ViewportConstrained);
>+
>+        if (scrollingNodeID || frameHostingNodeID || viewportConstrainedNodeID) {
>+            stream << " {";
>+            bool first = true;
>+            if (scrollingNodeID) {
>+                stream << "sc " << scrollingNodeID;
>+                first = false;
>+            }
>+
>+            if (frameHostingNodeID) {
>+                if (!first)
>+                    stream << ", ";
>+                stream << "fh " << frameHostingNodeID;
>+                first = false;
>+            }
>+
>+            if (viewportConstrainedNodeID) {
>+                if (!first)
>+                    stream << ", ";
>+                stream << "vc " << viewportConstrainedNodeID;
>+            }
>+
>+            stream << "}";
>+        }
>+    }
>     stream << " " << layer.name();
>     stream.nextLine();
> 
>diff --git a/Source/WebCore/rendering/RenderLayerBacking.cpp b/Source/WebCore/rendering/RenderLayerBacking.cpp
>index 818e7ba74dc31c5cf433cd5c58658e50d92a073f..f669c9122bc5b469f253921b9bb42524db0f9e5b 100644
>--- a/Source/WebCore/rendering/RenderLayerBacking.cpp
>+++ b/Source/WebCore/rendering/RenderLayerBacking.cpp
>@@ -783,7 +783,7 @@ bool RenderLayerBacking::updateConfiguration()
>         layerConfigChanged = true;
>     }
> #endif
>-    if (is<RenderWidget>(renderer()) && RenderLayerCompositor::parentFrameContentLayers(downcast<RenderWidget>(renderer()))) {
>+    if (is<RenderWidget>(renderer()) && compositor().parentFrameContentLayers(downcast<RenderWidget>(renderer()))) {
>         m_owningLayer.setNeedsCompositingGeometryUpdate();
>         layerConfigChanged = true;
>     }
>@@ -1769,7 +1769,7 @@ bool RenderLayerBacking::updateScrollingLayers(bool needsScrollingLayers)
> 
> void RenderLayerBacking::detachFromScrollingCoordinator(OptionSet<ScrollCoordinationRole> roles)
> {
>-    if (!m_scrollingNodeID && !m_viewportConstrainedNodeID)
>+    if (!m_scrollingNodeID && !m_frameHostingNodeID && !m_viewportConstrainedNodeID)
>         return;
> 
>     auto* scrollingCoordinator = m_owningLayer.page().scrollingCoordinator();
>diff --git a/Source/WebCore/rendering/RenderLayerCompositor.cpp b/Source/WebCore/rendering/RenderLayerCompositor.cpp
>index 28c82381964c0e5ee92fe5bf1ccd99be89ec691a..5b1ca4c95d6d1006e47428731493b4b083869d00 100644
>--- a/Source/WebCore/rendering/RenderLayerCompositor.cpp
>+++ b/Source/WebCore/rendering/RenderLayerCompositor.cpp
>@@ -1928,12 +1928,19 @@ String RenderLayerCompositor::layerTreeAsText(LayerTreeFlags flags)
>     return layerTreeText;
> }
> 
>+static RenderView* frameContentsRenderView(RenderWidget& renderer)
>+{
>+    if (auto* contentDocument = renderer.frameOwnerElement().contentDocument())
>+        return contentDocument->renderView();
>+
>+    return nullptr;
>+}
>+
> RenderLayerCompositor* RenderLayerCompositor::frameContentsCompositor(RenderWidget& renderer)
> {
>-    if (auto* contentDocument = renderer.frameOwnerElement().contentDocument()) {
>-        if (auto* view = contentDocument->renderView())
>-            return &view->compositor();
>-    }
>+    if (auto* view = frameContentsRenderView(renderer))
>+        return &view->compositor();
>+
>     return nullptr;
> }
> 
>@@ -1954,6 +1961,15 @@ bool RenderLayerCompositor::parentFrameContentLayers(RenderWidget& renderer)
>         hostingLayer->removeAllChildren();
>         hostingLayer->addChild(*rootLayer);
>     }
>+
>+    if (auto frameHostingNodeID = backing->scrollingNodeIDForRole(ScrollCoordinationRole::FrameHosting)) {
>+        auto* contentsRenderView = frameContentsRenderView(renderer);
>+        if (auto frameRootScrollingNodeID = contentsRenderView->frameView().scrollLayerID()) {
>+            if (auto* scrollingCoordinator = this->scrollingCoordinator())
>+                scrollingCoordinator->insertNode(ScrollingNodeType::Subframe, frameRootScrollingNodeID, frameHostingNodeID, 0);
>+        }
>+    }
>+
>     // FIXME: Why always return true and not just when the layers changed?
>     return true;
> }
>@@ -2843,6 +2859,25 @@ bool RenderLayerCompositor::useCoordinatedScrollingForLayer(const RenderLayer& l
>     return false;
> }
> 
>+bool RenderLayerCompositor::isLayerForIFrameWithScrollCoordinatedContents(const RenderLayer& layer) const
>+{
>+    if (!is<RenderWidget>(layer.renderer()))
>+        return false;
>+
>+    auto* contentDocument = downcast<RenderWidget>(layer.renderer()).frameOwnerElement().contentDocument();
>+    if (!contentDocument)
>+        return false;
>+
>+    auto* view = contentDocument->renderView();
>+    if (!view)
>+        return false;
>+
>+    if (auto* scrollingCoordinator = this->scrollingCoordinator())
>+        return scrollingCoordinator->coordinatesScrollingForFrameView(view->frameView());
>+
>+    return false;
>+}
>+
> bool RenderLayerCompositor::isRunningTransformAnimation(RenderLayerModelObject& renderer) const
> {
>     if (!(m_compositingTriggers & ChromeClient::AnimationTrigger))
>@@ -2859,8 +2894,7 @@ bool RenderLayerCompositor::isRunningTransformAnimation(RenderLayerModelObject&
> }
> 
> // If an element has negative z-index children, those children render in front of the 
>-// layer background, so we need an extra 'contents' layer for the foreground of the layer
>-// object.
>+// layer background, so we need an extra 'contents' layer for the foreground of the layer object.
> bool RenderLayerCompositor::needsContentsCompositingLayer(const RenderLayer& layer) const
> {
>     return layer.hasNegativeZOrderLayers();
>@@ -3534,7 +3568,7 @@ void RenderLayerCompositor::detachRootLayer()
> 
>     switch (m_rootLayerAttachment) {
>     case RootLayerAttachedViaEnclosingFrame: {
>-        // The layer will get unhooked up via RenderLayerBacking::updateGraphicsLayerConfiguration()
>+        // The layer will get unhooked up via RenderLayerBacking::updateConfiguration()
>         // for the frame's renderer in the parent document.
>         if (m_overflowControlsHostLayer)
>             m_overflowControlsHostLayer->removeFromParent();
>@@ -3543,6 +3577,11 @@ void RenderLayerCompositor::detachRootLayer()
> 
>         if (auto* ownerElement = m_renderView.document().ownerElement())
>             ownerElement->scheduleInvalidateStyleAndLayerComposition();
>+
>+        if (auto frameRootScrollingNodeID = m_renderView.frameView().scrollLayerID()) {
>+            if (auto* scrollingCoordinator = this->scrollingCoordinator())
>+                scrollingCoordinator->unparentNode(frameRootScrollingNodeID);
>+        }
>         break;
>     }
>     case RootLayerAttachedViaChromeClient: {
>@@ -3651,6 +3690,12 @@ void RenderLayerCompositor::updateScrollCoordinatedStatus(RenderLayer& layer, Op
>     if (useCoordinatedScrollingForLayer(layer))
>         coordinationRoles.add(ScrollCoordinationRole::Scrolling);
> 
>+    if (isLayerForIFrameWithScrollCoordinatedContents(layer)) {
>+        // We never expect a RenderIFrame to have scrollable overflow.
>+        ASSERT(!coordinationRoles.contains(ScrollCoordinationRole::Scrolling));
>+        coordinationRoles.add(ScrollCoordinationRole::FrameHosting);
>+    }
>+
>     if (layer.isComposited())
>         layer.backing()->setIsScrollCoordinatedWithViewportConstrainedRole(coordinationRoles.contains(ScrollCoordinationRole::ViewportConstrained));
> 
>@@ -3673,7 +3718,7 @@ void RenderLayerCompositor::removeFromScrollCoordinatedLayers(RenderLayer& layer
>     m_scrollCoordinatedLayers.remove(&layer);
>     m_scrollCoordinatedLayersNeedingUpdate.remove(&layer);
> 
>-    detachScrollCoordinatedLayer(layer, { ScrollCoordinationRole::Scrolling, ScrollCoordinationRole::ViewportConstrained });
>+    detachScrollCoordinatedLayer(layer, { ScrollCoordinationRole::Scrolling, ScrollCoordinationRole::ViewportConstrained, ScrollCoordinationRole::FrameHosting });
> }
> 
> FixedPositionViewportConstraints RenderLayerCompositor::computeFixedViewportConstraints(RenderLayer& layer) const
>@@ -3747,22 +3792,27 @@ static ScrollingNodeID enclosingScrollingNodeID(RenderLayer& layer, IncludeSelfO
>     return 0;
> }
> 
>-static ScrollingNodeID scrollCoordinatedAncestorInParentOfFrame(Frame& frame)
>+static Optional<ScrollingNodeID> scrollCoordinatedAncestorInParentOfFrame(Frame& frame)
> {
>     if (!frame.document() || !frame.view())
>-        return 0;
>+        return { };
> 
>     // Find the frame's enclosing layer in our render tree.
>     auto* ownerElement = frame.document()->ownerElement();
>     auto* frameRenderer = ownerElement ? ownerElement->renderer() : nullptr;
>-    if (!frameRenderer)
>-        return 0;
>+    if (!frameRenderer || !is<RenderWidget>(frameRenderer))
>+        return { };
> 
>-    auto* layerInParentDocument = frameRenderer->enclosingLayer();
>-    if (!layerInParentDocument)
>-        return 0;
>+    auto& widgetRenderer = downcast<RenderWidget>(*frameRenderer);
>+    if (!widgetRenderer.hasLayer() || !widgetRenderer.layer()->isComposited()) {
>+        LOG(Scrolling, "scrollCoordinatedAncestorInParentOfFrame: frame renderer has no layer or is not composited.");
>+        return { };
>+    }
>+
>+    if (auto frameHostingNodeID = widgetRenderer.layer()->backing()->scrollingNodeIDForRole(ScrollCoordinationRole::FrameHosting))
>+        return frameHostingNodeID;
> 
>-    return enclosingScrollingNodeID(*layerInParentDocument, IncludeSelf);
>+    return { };
> }
> 
> void RenderLayerCompositor::reattachSubframeScrollLayers()
>@@ -3784,11 +3834,13 @@ void RenderLayerCompositor::reattachSubframeScrollLayers()
>         if (!frameScrollingNodeID)
>             continue;
> 
>-        ScrollingNodeID parentNodeID = scrollCoordinatedAncestorInParentOfFrame(*child);
>-        if (!parentNodeID)
>+        auto parentNodeID = scrollCoordinatedAncestorInParentOfFrame(*child);
>+        if (!parentNodeID) {
>+            LOG(Scrolling, "RenderLayerCompositor %p reattachSubframeScrollLayers: failed to find scrolling node parent for frame with nodeID %llu.", this, frameScrollingNodeID);
>             continue;
>+        }
> 
>-        scrollingCoordinator->insertNode(child->isMainFrame() ? ScrollingNodeType::MainFrame : ScrollingNodeType::Subframe, frameScrollingNodeID, parentNodeID);
>+        scrollingCoordinator->insertNode(child->isMainFrame() ? ScrollingNodeType::MainFrame : ScrollingNodeType::Subframe, frameScrollingNodeID, parentNodeID.value());
>     }
> }
> 
>@@ -3809,7 +3861,7 @@ static inline ScrollCoordinationRole scrollCoordinationRoleForNodeType(Scrolling
>     return ScrollCoordinationRole::Scrolling;
> }
> 
>-ScrollingNodeID RenderLayerCompositor::attachScrollingNode(RenderLayer& layer, ScrollingNodeType nodeType, ScrollingNodeID parentNodeID)
>+ScrollingNodeID RenderLayerCompositor::attachScrollingNode(RenderLayer& layer, ScrollingNodeType nodeType, Optional<ScrollingNodeID> parentNodeID)
> {
>     auto* scrollingCoordinator = this->scrollingCoordinator();
>     auto* backing = layer.backing();
>@@ -3823,13 +3875,19 @@ ScrollingNodeID RenderLayerCompositor::attachScrollingNode(RenderLayer& layer, S
>     if (!nodeID)
>         nodeID = scrollingCoordinator->uniqueScrollingNodeID();
> 
>-    nodeID = scrollingCoordinator->insertNode(nodeType, nodeID, parentNodeID);
>+    LOG_WITH_STREAM(Scrolling, stream << "RenderLayerCompositor " << this << " attachScrollingNode " << nodeID << " type " << nodeType << " parent " << parentNodeID.valueOr(0));
>+
>+    if (nodeType == ScrollingNodeType::Subframe && !parentNodeID)
>+        nodeID = scrollingCoordinator->createNode(nodeType, nodeID);
>+    else
>+        nodeID = scrollingCoordinator->insertNode(nodeType, nodeID, parentNodeID.valueOr(0));
>+
>     if (!nodeID)
>         return 0;
> 
>     backing->setScrollingNodeIDForRole(nodeID, role);
>     m_scrollingNodeToLayerMap.add(nodeID, &layer);
>-    
>+
>     return nodeID;
> }
> 
>@@ -3869,7 +3927,7 @@ void RenderLayerCompositor::detachScrollCoordinatedLayer(RenderLayer& layer, Opt
>     backing->detachFromScrollingCoordinator(roles);
> }
> 
>-void RenderLayerCompositor::updateScrollCoordinationForThisFrame(ScrollingNodeID parentNodeID, OptionSet<ScrollingNodeChangeFlags> changes)
>+void RenderLayerCompositor::updateScrollCoordinationForThisFrame(Optional<ScrollingNodeID> parentNodeID, OptionSet<ScrollingNodeChangeFlags> changes)
> {
>     auto* scrollingCoordinator = this->scrollingCoordinator();
>     FrameView& frameView = m_renderView.frameView();
>@@ -3907,10 +3965,7 @@ void RenderLayerCompositor::updateScrollCoordinatedLayer(RenderLayer& layer, Opt
>         return;
> 
>     if (!m_renderView.frame().isMainFrame()) {
>-        ScrollingNodeID parentDocumentHostingNodeID = scrollCoordinatedAncestorInParentOfFrame(m_renderView.frame());
>-        if (!parentDocumentHostingNodeID)
>-            return;
>-
>+        auto parentDocumentHostingNodeID = scrollCoordinatedAncestorInParentOfFrame(m_renderView.frame());
>         updateScrollCoordinationForThisFrame(parentDocumentHostingNodeID, changes);
>         if (!(roles.contains(ScrollCoordinationRole::ViewportConstrained)) && isRenderViewLayer)
>             return;
>diff --git a/Source/WebCore/rendering/RenderLayerCompositor.h b/Source/WebCore/rendering/RenderLayerCompositor.h
>index c33f99341162639c5f4f1d4d59358ec9964b989f..9c94bdf072839387280ab15dc3818d5b6fcc4ec4 100644
>--- a/Source/WebCore/rendering/RenderLayerCompositor.h
>+++ b/Source/WebCore/rendering/RenderLayerCompositor.h
>@@ -272,7 +272,7 @@ public:
>     
>     static RenderLayerCompositor* frameContentsCompositor(RenderWidget&);
>     // Return true if the layers changed.
>-    static bool parentFrameContentLayers(RenderWidget&);
>+    bool parentFrameContentLayers(RenderWidget&);
> 
>     // Update the geometry of the layers used for clipping and scrolling in frames.
>     void frameViewDidChangeLocation(const IntPoint& contentsOffset);
>@@ -326,6 +326,7 @@ public:
>     void removeFromScrollCoordinatedLayers(RenderLayer&);
> 
>     bool useCoordinatedScrollingForLayer(const RenderLayer&) const;
>+    bool isLayerForIFrameWithScrollCoordinatedContents(const RenderLayer&) const;
> 
>     void willRemoveScrollingLayerWithBacking(RenderLayer&, RenderLayerBacking&);
>     void didAddScrollingLayer(RenderLayer&);
>@@ -476,8 +477,8 @@ private:
> 
>     void updateCustomLayersAfterFlush();
> 
>-    void updateScrollCoordinationForThisFrame(ScrollingNodeID, OptionSet<ScrollingNodeChangeFlags>);
>-    ScrollingNodeID attachScrollingNode(RenderLayer&, ScrollingNodeType, ScrollingNodeID parentNodeID);
>+    void updateScrollCoordinationForThisFrame(Optional<ScrollingNodeID>, OptionSet<ScrollingNodeChangeFlags>);
>+    ScrollingNodeID attachScrollingNode(RenderLayer&, ScrollingNodeType, Optional<ScrollingNodeID> parentNodeID);
>     void updateScrollCoordinatedLayer(RenderLayer&, OptionSet<ScrollCoordinationRole>, OptionSet<ScrollingNodeChangeFlags>);
>     void detachScrollCoordinatedLayer(RenderLayer&, OptionSet<ScrollCoordinationRole>);
>     void detachScrollCoordinatedLayerWithRole(RenderLayer&, ScrollingCoordinator&, ScrollCoordinationRole);
>diff --git a/Source/WebCore/testing/Internals.cpp b/Source/WebCore/testing/Internals.cpp
>index 1c84704b7b3965298a872894bcfad2e12b4da602..0d70981ced8abc8cfcbe85288f1b2a5f021adcc7 100644
>--- a/Source/WebCore/testing/Internals.cpp
>+++ b/Source/WebCore/testing/Internals.cpp
>@@ -2568,6 +2568,8 @@ ExceptionOr<String> Internals::scrollingStateTreeAsText() const
>     if (!document || !document->frame())
>         return Exception { InvalidAccessError };
> 
>+    document->updateLayoutIgnorePendingStylesheets();
>+
>     Page* page = document->page();
>     if (!page)
>         return String();
>diff --git a/Source/WebKit/Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp b/Source/WebKit/Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp
>index 30221e478631a6359545baed5b7d7266bc5ef9df..03a9f8f2009339de081668d3b52aaf34e4a8004e 100644
>--- a/Source/WebKit/Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp
>+++ b/Source/WebKit/Shared/RemoteLayerTree/RemoteScrollingCoordinatorTransaction.cpp
>@@ -524,7 +524,11 @@ static void dump(TextStream& ts, const ScrollingStateScrollingNode& node, bool c
>     if (!changedPropertiesOnly || node.hasChangedProperty(ScrollingStateScrollingNode::ScrolledContentsLayer))
>         ts.dumpProperty("scrolled-contents-layer", static_cast<GraphicsLayer::PlatformLayerID>(node.scrolledContentsLayer()));
> }
>-    
>+
>+static void dump(TextStream& ts, const ScrollingStateFrameHostingNode& node, bool changedPropertiesOnly)
>+{
>+}
>+
> static void dump(TextStream& ts, const ScrollingStateFrameScrollingNode& node, bool changedPropertiesOnly)
> {
>     dump(ts, static_cast<const ScrollingStateScrollingNode&>(node), changedPropertiesOnly);
>diff --git a/LayoutTests/ChangeLog b/LayoutTests/ChangeLog
>index e2996664a14d7f60c774e7e56c5389af25f5db55..62e952e651edad91c9b17c3a1a40ac9719757f08 100644
>--- a/LayoutTests/ChangeLog
>+++ b/LayoutTests/ChangeLog
>@@ -1,3 +1,27 @@
>+2019-01-26  Simon Fraser  <simon.fraser@apple.com>
>+
>+        Have composited RenderIFrame layers make FrameHosting scrolling tree nodes to parent the iframe's scrolling node
>+        https://bugs.webkit.org/show_bug.cgi?id=193879
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        New test results with FrameHosting nodes.
>+
>+        * platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt:
>+        * platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt:
>+        * platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt:
>+        * platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt:
>+        * platform/ios-wk2/scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt:
>+        * platform/ios-wk2/scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt:
>+        * platform/ios-wk2/scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt:
>+        * scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt:
>+        * scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt:
>+        * scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt:
>+        * scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt:
>+        * scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt:
>+        * scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt:
>+        * scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt:
>+
> 2019-01-26  Devin Rousso  <drousso@apple.com>
> 
>         Web Inspector: handle CSS Color 4 color syntaxes
>diff --git a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt
>index 4cfaf4b66bc7d4bb43754d7188d0d04763c7b5e0..27ca443f3085870d17924c9b6ba272cb58fa4611 100644
>--- a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt
>@@ -13,51 +13,55 @@
>   (max layout viewport origin (0,416))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 500 300)
>-      (contents size 500 420)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 1)
>-        (vertical scroll elasticity 1)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 500x300)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,120))
>-      (behavior for fixed 0)
>-      (children 2
>-        (Overflow scrolling node
>-          (scrollable area size 400 300)
>-          (contents size 400 1760)
>+    (Frame hosting node
>+      (children 1
>+        (Frame scrolling node
>+          (scrollable area size 500 300)
>+          (contents size 500 420)
>           (scrollable area parameters 
>             (horizontal scroll elasticity 1)
>             (vertical scroll elasticity 1)
>             (horizontal scrollbar mode 0)
>             (vertical scrollbar mode 0))
>-          (children 1
>+          (visual viewport enabled 1)
>+          (layout viewport at (0,0) size 500x300)
>+          (min layout viewport origin (0,0))
>+          (max layout viewport origin (0,120))
>+          (behavior for fixed 0)
>+          (children 2
>+            (Overflow scrolling node
>+              (scrollable area size 400 300)
>+              (contents size 400 1760)
>+              (scrollable area parameters 
>+                (horizontal scroll elasticity 1)
>+                (vertical scroll elasticity 1)
>+                (horizontal scrollbar mode 0)
>+                (vertical scrollbar mode 0))
>+              (children 1
>+                (Sticky node
>+                  (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>+                  (top offset 10.00)
>+                  (bottom offset 10.00)
>+                  (containing block rect at (2,2) size 400x1760)
>+                  (sticky box rect at (0,830) size 100x100)
>+                  (constraining rect at (0,0) size 400x300)
>+                  (sticky offset at last layout width=0 height=-640)
>+                  (layer position at last layout (0,190))
>+                )
>+              )
>+            )
>             (Sticky node
>               (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>               (top offset 10.00)
>               (bottom offset 10.00)
>-              (containing block rect at (2,2) size 400x1760)
>-              (sticky box rect at (0,830) size 100x100)
>-              (constraining rect at (0,0) size 400x300)
>-              (sticky offset at last layout width=0 height=-640)
>-              (layer position at last layout (0,190))
>+              (containing block rect at (8,8) size 484x404)
>+              (sticky box rect at (8,312) size 100x100)
>+              (constraining rect at (0,0) size 500x300)
>+              (sticky offset at last layout width=0 height=-122)
>+              (layer position at last layout (8,190))
>             )
>           )
>         )
>-        (Sticky node
>-          (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>-          (top offset 10.00)
>-          (bottom offset 10.00)
>-          (containing block rect at (8,8) size 484x404)
>-          (sticky box rect at (8,312) size 100x100)
>-          (constraining rect at (0,0) size 500x300)
>-          (sticky offset at last layout width=0 height=-122)
>-          (layer position at last layout (8,190))
>-        )
>       )
>     )
>   )
>diff --git a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt
>index c90398275b414d3f886a2b2d1ede35015a891996..9af13737c4061f56649588d52b6822e85181b442 100644
>--- a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt
>@@ -18,51 +18,55 @@
>       (viewport rect at last layout at (0,0) size 800x600)
>       (layer position at last layout (8,10))
>       (children 1
>-        (Frame scrolling node
>-          (scrollable area size 500 300)
>-          (contents size 500 420)
>-          (scrollable area parameters 
>-            (horizontal scroll elasticity 1)
>-            (vertical scroll elasticity 1)
>-            (horizontal scrollbar mode 1)
>-            (vertical scrollbar mode 1))
>-          (visual viewport enabled 1)
>-          (layout viewport at (0,0) size 500x300)
>-          (min layout viewport origin (0,0))
>-          (max layout viewport origin (0,120))
>-          (behavior for fixed 0)
>-          (children 2
>-            (Overflow scrolling node
>-              (scrollable area size 400 300)
>-              (contents size 400 1760)
>+        (Frame hosting node
>+          (children 1
>+            (Frame scrolling node
>+              (scrollable area size 500 300)
>+              (contents size 500 420)
>               (scrollable area parameters 
>                 (horizontal scroll elasticity 1)
>                 (vertical scroll elasticity 1)
>-                (horizontal scrollbar mode 0)
>-                (vertical scrollbar mode 0))
>-              (children 1
>+                (horizontal scrollbar mode 1)
>+                (vertical scrollbar mode 1))
>+              (visual viewport enabled 1)
>+              (layout viewport at (0,0) size 500x300)
>+              (min layout viewport origin (0,0))
>+              (max layout viewport origin (0,120))
>+              (behavior for fixed 0)
>+              (children 2
>+                (Overflow scrolling node
>+                  (scrollable area size 400 300)
>+                  (contents size 400 1760)
>+                  (scrollable area parameters 
>+                    (horizontal scroll elasticity 1)
>+                    (vertical scroll elasticity 1)
>+                    (horizontal scrollbar mode 0)
>+                    (vertical scrollbar mode 0))
>+                  (children 1
>+                    (Sticky node
>+                      (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>+                      (top offset 10.00)
>+                      (bottom offset 10.00)
>+                      (containing block rect at (2,2) size 400x1760)
>+                      (sticky box rect at (0,830) size 100x100)
>+                      (constraining rect at (0,0) size 400x300)
>+                      (sticky offset at last layout width=0 height=-640)
>+                      (layer position at last layout (0,190))
>+                    )
>+                  )
>+                )
>                 (Sticky node
>                   (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>                   (top offset 10.00)
>                   (bottom offset 10.00)
>-                  (containing block rect at (2,2) size 400x1760)
>-                  (sticky box rect at (0,830) size 100x100)
>-                  (constraining rect at (0,0) size 400x300)
>-                  (sticky offset at last layout width=0 height=-640)
>-                  (layer position at last layout (0,190))
>+                  (containing block rect at (8,8) size 484x404)
>+                  (sticky box rect at (8,312) size 100x100)
>+                  (constraining rect at (0,0) size 500x300)
>+                  (sticky offset at last layout width=0 height=-122)
>+                  (layer position at last layout (8,190))
>                 )
>               )
>             )
>-            (Sticky node
>-              (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>-              (top offset 10.00)
>-              (bottom offset 10.00)
>-              (containing block rect at (8,8) size 484x404)
>-              (sticky box rect at (8,312) size 100x100)
>-              (constraining rect at (0,0) size 500x300)
>-              (sticky offset at last layout width=0 height=-122)
>-              (layer position at last layout (8,190))
>-            )
>           )
>         )
>       )
>diff --git a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt
>index cca344843769b92ec67a4b2105c440e8d9395b86..28fc30e6f6f78a501f4b2e098b8a86445bca0bc9 100644
>--- a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt
>@@ -18,51 +18,55 @@
>       (viewport rect at last layout at (0,0) size 800x600)
>       (layer position at last layout (8,0))
>       (children 1
>-        (Frame scrolling node
>-          (scrollable area size 500 300)
>-          (contents size 500 420)
>-          (scrollable area parameters 
>-            (horizontal scroll elasticity 1)
>-            (vertical scroll elasticity 1)
>-            (horizontal scrollbar mode 0)
>-            (vertical scrollbar mode 0))
>-          (visual viewport enabled 1)
>-          (layout viewport at (0,0) size 500x300)
>-          (min layout viewport origin (0,0))
>-          (max layout viewport origin (0,120))
>-          (behavior for fixed 0)
>-          (children 2
>-            (Overflow scrolling node
>-              (scrollable area size 400 300)
>-              (contents size 400 1760)
>+        (Frame hosting node
>+          (children 1
>+            (Frame scrolling node
>+              (scrollable area size 500 300)
>+              (contents size 500 420)
>               (scrollable area parameters 
>                 (horizontal scroll elasticity 1)
>                 (vertical scroll elasticity 1)
>                 (horizontal scrollbar mode 0)
>                 (vertical scrollbar mode 0))
>-              (children 1
>+              (visual viewport enabled 1)
>+              (layout viewport at (0,0) size 500x300)
>+              (min layout viewport origin (0,0))
>+              (max layout viewport origin (0,120))
>+              (behavior for fixed 0)
>+              (children 2
>+                (Overflow scrolling node
>+                  (scrollable area size 400 300)
>+                  (contents size 400 1760)
>+                  (scrollable area parameters 
>+                    (horizontal scroll elasticity 1)
>+                    (vertical scroll elasticity 1)
>+                    (horizontal scrollbar mode 0)
>+                    (vertical scrollbar mode 0))
>+                  (children 1
>+                    (Sticky node
>+                      (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>+                      (top offset 10.00)
>+                      (bottom offset 10.00)
>+                      (containing block rect at (2,2) size 400x1760)
>+                      (sticky box rect at (0,830) size 100x100)
>+                      (constraining rect at (0,0) size 400x300)
>+                      (sticky offset at last layout width=0 height=-640)
>+                      (layer position at last layout (0,190))
>+                    )
>+                  )
>+                )
>                 (Sticky node
>                   (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>                   (top offset 10.00)
>                   (bottom offset 10.00)
>-                  (containing block rect at (2,2) size 400x1760)
>-                  (sticky box rect at (0,830) size 100x100)
>-                  (constraining rect at (0,0) size 400x300)
>-                  (sticky offset at last layout width=0 height=-640)
>-                  (layer position at last layout (0,190))
>+                  (containing block rect at (8,8) size 484x404)
>+                  (sticky box rect at (8,312) size 100x100)
>+                  (constraining rect at (0,0) size 500x300)
>+                  (sticky offset at last layout width=0 height=-122)
>+                  (layer position at last layout (8,190))
>                 )
>               )
>             )
>-            (Sticky node
>-              (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>-              (top offset 10.00)
>-              (bottom offset 10.00)
>-              (containing block rect at (8,8) size 484x404)
>-              (sticky box rect at (8,312) size 100x100)
>-              (constraining rect at (0,0) size 500x300)
>-              (sticky offset at last layout width=0 height=-122)
>-              (layer position at last layout (8,190))
>-            )
>           )
>         )
>       )
>diff --git a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt
>index ff36fdeafccbdac0d22a817133b487e78a8430ee..aa54c26880f1aa03a22932b822533ff704883aed 100644
>--- a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt
>@@ -13,51 +13,55 @@
>   (max layout viewport origin (0,416))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 500 300)
>-      (contents size 500 420)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 1)
>-        (vertical scroll elasticity 1)
>-        (horizontal scrollbar mode 1)
>-        (vertical scrollbar mode 1))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 500x300)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,120))
>-      (behavior for fixed 0)
>-      (children 2
>-        (Overflow scrolling node
>-          (scrollable area size 400 300)
>-          (contents size 400 1760)
>+    (Frame hosting node
>+      (children 1
>+        (Frame scrolling node
>+          (scrollable area size 500 300)
>+          (contents size 500 420)
>           (scrollable area parameters 
>             (horizontal scroll elasticity 1)
>             (vertical scroll elasticity 1)
>-            (horizontal scrollbar mode 0)
>-            (vertical scrollbar mode 0))
>-          (children 1
>+            (horizontal scrollbar mode 1)
>+            (vertical scrollbar mode 1))
>+          (visual viewport enabled 1)
>+          (layout viewport at (0,0) size 500x300)
>+          (min layout viewport origin (0,0))
>+          (max layout viewport origin (0,120))
>+          (behavior for fixed 0)
>+          (children 2
>+            (Overflow scrolling node
>+              (scrollable area size 400 300)
>+              (contents size 400 1760)
>+              (scrollable area parameters 
>+                (horizontal scroll elasticity 1)
>+                (vertical scroll elasticity 1)
>+                (horizontal scrollbar mode 0)
>+                (vertical scrollbar mode 0))
>+              (children 1
>+                (Sticky node
>+                  (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>+                  (top offset 10.00)
>+                  (bottom offset 10.00)
>+                  (containing block rect at (2,2) size 400x1760)
>+                  (sticky box rect at (0,830) size 100x100)
>+                  (constraining rect at (0,0) size 400x300)
>+                  (sticky offset at last layout width=0 height=-640)
>+                  (layer position at last layout (0,190))
>+                )
>+              )
>+            )
>             (Sticky node
>               (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>               (top offset 10.00)
>               (bottom offset 10.00)
>-              (containing block rect at (2,2) size 400x1760)
>-              (sticky box rect at (0,830) size 100x100)
>-              (constraining rect at (0,0) size 400x300)
>-              (sticky offset at last layout width=0 height=-640)
>-              (layer position at last layout (0,190))
>+              (containing block rect at (8,8) size 484x404)
>+              (sticky box rect at (8,312) size 100x100)
>+              (constraining rect at (0,0) size 500x300)
>+              (sticky offset at last layout width=0 height=-122)
>+              (layer position at last layout (8,190))
>             )
>           )
>         )
>-        (Sticky node
>-          (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>-          (top offset 10.00)
>-          (bottom offset 10.00)
>-          (containing block rect at (8,8) size 484x404)
>-          (sticky box rect at (8,312) size 100x100)
>-          (constraining rect at (0,0) size 500x300)
>-          (sticky offset at last layout width=0 height=-122)
>-          (layer position at last layout (8,190))
>-        )
>       )
>     )
>   )
>diff --git a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt
>index bd1e25080e1060b8663aeba19123e32240d1b127..df5af7a160cb64747ba1d17182610e31fd837f59 100644
>--- a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt
>@@ -14,26 +14,30 @@
>   (max layout viewport origin (0,57))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 480 400)
>-      (contents size 480 1016)
>-      (requested scroll position 0 120)
>-      (requested scroll position represents programmatic scroll 1)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 1)
>-        (vertical scroll elasticity 1)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,120) size 480x400)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,616))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>       (children 1
>-        (Fixed node
>-          (anchor edges: AnchorEdgeLeft AnchorEdgeTop)
>-          (viewport rect at last layout at (0,120) size 480x400)
>-          (layer position at last layout (10,130))
>+        (Frame scrolling node
>+          (scrollable area size 480 400)
>+          (contents size 480 1016)
>+          (requested scroll position 0 120)
>+          (requested scroll position represents programmatic scroll 1)
>+          (scrollable area parameters 
>+            (horizontal scroll elasticity 1)
>+            (vertical scroll elasticity 1)
>+            (horizontal scrollbar mode 0)
>+            (vertical scrollbar mode 0))
>+          (visual viewport enabled 1)
>+          (layout viewport at (0,120) size 480x400)
>+          (min layout viewport origin (0,0))
>+          (max layout viewport origin (0,616))
>+          (behavior for fixed 0)
>+          (children 1
>+            (Fixed node
>+              (anchor edges: AnchorEdgeLeft AnchorEdgeTop)
>+              (viewport rect at last layout at (0,120) size 480x400)
>+              (layer position at last layout (10,130))
>+            )
>+          )
>         )
>       )
>     )
>diff --git a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt
>index 4b34bf64bfc00b3034e664f899880ed18f3e9fb3..deb8cdd941a4ebbf0ba554354de683b5b5c2cc64 100644
>--- a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt
>@@ -14,19 +14,23 @@
>   (max layout viewport origin (0,0))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 100 200)
>-      (contents size 308 416)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 1)
>-        (vertical scroll elasticity 1)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 100x200)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (208,216))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>+      (children 1
>+        (Frame scrolling node
>+          (scrollable area size 100 200)
>+          (contents size 308 416)
>+          (scrollable area parameters 
>+            (horizontal scroll elasticity 1)
>+            (vertical scroll elasticity 1)
>+            (horizontal scrollbar mode 0)
>+            (vertical scrollbar mode 0))
>+          (visual viewport enabled 1)
>+          (layout viewport at (0,0) size 100x200)
>+          (min layout viewport origin (0,0))
>+          (max layout viewport origin (208,216))
>+          (behavior for fixed 0)
>+        )
>+      )
>     )
>   )
> )
>diff --git a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt
>index 69475242e43eae0b23338af07462676ef5699f39..c4516290f547568e7881177e9dbfae39dfcff8f2 100644
>--- a/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt
>@@ -16,33 +16,41 @@ Scrolling tree on non-scrollable
>   (max layout viewport origin (0,45))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 600 500)
>-      (contents size 600 1024)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 1)
>-        (vertical scroll elasticity 1)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 600x500)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,524))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>       (children 1
>         (Frame scrolling node
>-          (scrollable area size 500 400)
>-          (contents size 500 1024)
>+          (scrollable area size 600 500)
>+          (contents size 600 1024)
>           (scrollable area parameters 
>             (horizontal scroll elasticity 1)
>             (vertical scroll elasticity 1)
>             (horizontal scrollbar mode 0)
>             (vertical scrollbar mode 0))
>           (visual viewport enabled 1)
>-          (layout viewport at (0,0) size 500x400)
>+          (layout viewport at (0,0) size 600x500)
>           (min layout viewport origin (0,0))
>-          (max layout viewport origin (0,624))
>+          (max layout viewport origin (0,524))
>           (behavior for fixed 0)
>+          (children 1
>+            (Frame hosting node
>+              (children 1
>+                (Frame scrolling node
>+                  (scrollable area size 500 400)
>+                  (contents size 500 1024)
>+                  (scrollable area parameters 
>+                    (horizontal scroll elasticity 1)
>+                    (vertical scroll elasticity 1)
>+                    (horizontal scrollbar mode 0)
>+                    (vertical scrollbar mode 0))
>+                  (visual viewport enabled 1)
>+                  (layout viewport at (0,0) size 500x400)
>+                  (min layout viewport origin (0,0))
>+                  (max layout viewport origin (0,624))
>+                  (behavior for fixed 0)
>+                )
>+              )
>+            )
>+          )
>         )
>       )
>     )
>@@ -54,7 +62,7 @@ Scrolling tree on scrollable
> 
> (Frame scrolling node
>   (scrollable area size 800 600)
>-  (contents size 800 1333)
>+  (contents size 800 1445)
>   (scrollable area parameters 
>     (horizontal scroll elasticity 1)
>     (vertical scroll elasticity 1)
>@@ -63,36 +71,44 @@ Scrolling tree on scrollable
>   (visual viewport enabled 1)
>   (layout viewport at (0,0) size 800x600)
>   (min layout viewport origin (0,0))
>-  (max layout viewport origin (0,733))
>+  (max layout viewport origin (0,845))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 600 500)
>-      (contents size 600 500)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 1)
>-        (vertical scroll elasticity 1)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 600x500)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,0))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>       (children 1
>         (Frame scrolling node
>-          (scrollable area size 500 400)
>-          (contents size 500 1024)
>+          (scrollable area size 600 500)
>+          (contents size 600 500)
>           (scrollable area parameters 
>             (horizontal scroll elasticity 1)
>             (vertical scroll elasticity 1)
>             (horizontal scrollbar mode 0)
>             (vertical scrollbar mode 0))
>           (visual viewport enabled 1)
>-          (layout viewport at (0,0) size 500x400)
>+          (layout viewport at (0,0) size 600x500)
>           (min layout viewport origin (0,0))
>-          (max layout viewport origin (0,624))
>+          (max layout viewport origin (0,0))
>           (behavior for fixed 0)
>+          (children 1
>+            (Frame hosting node
>+              (children 1
>+                (Frame scrolling node
>+                  (scrollable area size 500 400)
>+                  (contents size 500 1024)
>+                  (scrollable area parameters 
>+                    (horizontal scroll elasticity 1)
>+                    (vertical scroll elasticity 1)
>+                    (horizontal scrollbar mode 0)
>+                    (vertical scrollbar mode 0))
>+                  (visual viewport enabled 1)
>+                  (layout viewport at (0,0) size 500x400)
>+                  (min layout viewport origin (0,0))
>+                  (max layout viewport origin (0,624))
>+                  (behavior for fixed 0)
>+                )
>+              )
>+            )
>+          )
>         )
>       )
>     )
>diff --git a/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt b/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt
>index 51c67f6ce67b8ff8b919d6487c662babf2b95363..35ba543692421457933d693581d42102b79999f5 100644
>--- a/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt
>+++ b/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-expected.txt
>@@ -16,30 +16,34 @@
>     at (45,47) size 404x304)
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 485 300)
>-      (contents size 485 420)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 0)
>-        (vertical scroll elasticity 0)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0)
>-        (has enabled vertical scrollbar 1))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 485x300)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,120))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>       (children 1
>-        (Sticky node
>-          (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>-          (top offset 10.00)
>-          (bottom offset 10.00)
>-          (containing block rect at (8,8) size 469x404)
>-          (sticky box rect at (8,312) size 100x100)
>-          (constraining rect at (0,0) size 485x300)
>-          (sticky offset at last layout width=0 height=-122)
>-          (layer position at last layout (8,190))
>+        (Frame scrolling node
>+          (scrollable area size 485 300)
>+          (contents size 485 420)
>+          (scrollable area parameters 
>+            (horizontal scroll elasticity 0)
>+            (vertical scroll elasticity 0)
>+            (horizontal scrollbar mode 0)
>+            (vertical scrollbar mode 0)
>+            (has enabled vertical scrollbar 1))
>+          (visual viewport enabled 1)
>+          (layout viewport at (0,0) size 485x300)
>+          (min layout viewport origin (0,0))
>+          (max layout viewport origin (0,120))
>+          (behavior for fixed 0)
>+          (children 1
>+            (Sticky node
>+              (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>+              (top offset 10.00)
>+              (bottom offset 10.00)
>+              (containing block rect at (8,8) size 469x404)
>+              (sticky box rect at (8,312) size 100x100)
>+              (constraining rect at (0,0) size 485x300)
>+              (sticky offset at last layout width=0 height=-122)
>+              (layer position at last layout (8,190))
>+            )
>+          )
>         )
>       )
>     )
>diff --git a/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt b/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt
>index 2f4a32a0dbe0e62f8b435fa91b7d01c127d149b4..ef8d8343298dc6821d944ff0d81f854103a7912e 100644
>--- a/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt
>+++ b/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-gain-scrolling-ancestor-expected.txt
>@@ -21,29 +21,33 @@
>       (viewport rect at last layout at (0,0) size 785x600)
>       (layer position at last layout (8,10))
>       (children 1
>-        (Frame scrolling node
>-          (scrollable area size 500 300)
>-          (contents size 500 420)
>-          (scrollable area parameters 
>-            (horizontal scroll elasticity 0)
>-            (vertical scroll elasticity 0)
>-            (horizontal scrollbar mode 1)
>-            (vertical scrollbar mode 1))
>-          (visual viewport enabled 1)
>-          (layout viewport at (0,0) size 500x300)
>-          (min layout viewport origin (0,0))
>-          (max layout viewport origin (0,120))
>-          (behavior for fixed 0)
>+        (Frame hosting node
>           (children 1
>-            (Sticky node
>-              (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>-              (top offset 10.00)
>-              (bottom offset 10.00)
>-              (containing block rect at (8,8) size 484x404)
>-              (sticky box rect at (8,312) size 100x100)
>-              (constraining rect at (0,0) size 500x300)
>-              (sticky offset at last layout width=0 height=-122)
>-              (layer position at last layout (8,190))
>+            (Frame scrolling node
>+              (scrollable area size 500 300)
>+              (contents size 500 420)
>+              (scrollable area parameters 
>+                (horizontal scroll elasticity 0)
>+                (vertical scroll elasticity 0)
>+                (horizontal scrollbar mode 1)
>+                (vertical scrollbar mode 1))
>+              (visual viewport enabled 1)
>+              (layout viewport at (0,0) size 500x300)
>+              (min layout viewport origin (0,0))
>+              (max layout viewport origin (0,120))
>+              (behavior for fixed 0)
>+              (children 1
>+                (Sticky node
>+                  (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>+                  (top offset 10.00)
>+                  (bottom offset 10.00)
>+                  (containing block rect at (8,8) size 484x404)
>+                  (sticky box rect at (8,312) size 100x100)
>+                  (constraining rect at (0,0) size 500x300)
>+                  (sticky offset at last layout width=0 height=-122)
>+                  (layer position at last layout (8,190))
>+                )
>+              )
>             )
>           )
>         )
>diff --git a/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt b/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt
>index b67332d9fca632dd86c832b5553a55afd1b793a4..e0e494ef5bc96be4dfaef930c4c5fde3232317b0 100644
>--- a/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt
>+++ b/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-in-fixed-expected.txt
>@@ -21,30 +21,34 @@
>       (viewport rect at last layout at (0,0) size 785x600)
>       (layer position at last layout (8,0))
>       (children 1
>-        (Frame scrolling node
>-          (scrollable area size 485 300)
>-          (contents size 485 420)
>-          (scrollable area parameters 
>-            (horizontal scroll elasticity 0)
>-            (vertical scroll elasticity 0)
>-            (horizontal scrollbar mode 0)
>-            (vertical scrollbar mode 0)
>-            (has enabled vertical scrollbar 1))
>-          (visual viewport enabled 1)
>-          (layout viewport at (0,0) size 485x300)
>-          (min layout viewport origin (0,0))
>-          (max layout viewport origin (0,120))
>-          (behavior for fixed 0)
>+        (Frame hosting node
>           (children 1
>-            (Sticky node
>-              (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>-              (top offset 10.00)
>-              (bottom offset 10.00)
>-              (containing block rect at (8,8) size 469x404)
>-              (sticky box rect at (8,312) size 100x100)
>-              (constraining rect at (0,0) size 485x300)
>-              (sticky offset at last layout width=0 height=-122)
>-              (layer position at last layout (8,190))
>+            (Frame scrolling node
>+              (scrollable area size 485 300)
>+              (contents size 485 420)
>+              (scrollable area parameters 
>+                (horizontal scroll elasticity 0)
>+                (vertical scroll elasticity 0)
>+                (horizontal scrollbar mode 0)
>+                (vertical scrollbar mode 0)
>+                (has enabled vertical scrollbar 1))
>+              (visual viewport enabled 1)
>+              (layout viewport at (0,0) size 485x300)
>+              (min layout viewport origin (0,0))
>+              (max layout viewport origin (0,120))
>+              (behavior for fixed 0)
>+              (children 1
>+                (Sticky node
>+                  (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>+                  (top offset 10.00)
>+                  (bottom offset 10.00)
>+                  (containing block rect at (8,8) size 469x404)
>+                  (sticky box rect at (8,312) size 100x100)
>+                  (constraining rect at (0,0) size 485x300)
>+                  (sticky offset at last layout width=0 height=-122)
>+                  (layer position at last layout (8,190))
>+                )
>+              )
>             )
>           )
>         )
>diff --git a/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt b/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt
>index 9a9f562b360aec5e25df70aaa37fe54dd17acefd..0d27984f8a6a44121cb383e33324b31cadb0e43c 100644
>--- a/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt
>+++ b/LayoutTests/scrollingcoordinator/scrolling-tree/coordinated-frame-lose-scrolling-ancestor-expected.txt
>@@ -16,29 +16,33 @@
>     at (45,47) size 404x304)
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 500 300)
>-      (contents size 500 420)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 0)
>-        (vertical scroll elasticity 0)
>-        (horizontal scrollbar mode 1)
>-        (vertical scrollbar mode 1))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 500x300)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,120))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>       (children 1
>-        (Sticky node
>-          (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>-          (top offset 10.00)
>-          (bottom offset 10.00)
>-          (containing block rect at (8,8) size 484x404)
>-          (sticky box rect at (8,312) size 100x100)
>-          (constraining rect at (0,0) size 500x300)
>-          (sticky offset at last layout width=0 height=-122)
>-          (layer position at last layout (8,190))
>+        (Frame scrolling node
>+          (scrollable area size 500 300)
>+          (contents size 500 420)
>+          (scrollable area parameters 
>+            (horizontal scroll elasticity 0)
>+            (vertical scroll elasticity 0)
>+            (horizontal scrollbar mode 1)
>+            (vertical scrollbar mode 1))
>+          (visual viewport enabled 1)
>+          (layout viewport at (0,0) size 500x300)
>+          (min layout viewport origin (0,0))
>+          (max layout viewport origin (0,120))
>+          (behavior for fixed 0)
>+          (children 1
>+            (Sticky node
>+              (anchor edges: AnchorEdgeTop AnchorEdgeBottom)
>+              (top offset 10.00)
>+              (bottom offset 10.00)
>+              (containing block rect at (8,8) size 484x404)
>+              (sticky box rect at (8,312) size 100x100)
>+              (constraining rect at (0,0) size 500x300)
>+              (sticky offset at last layout width=0 height=-122)
>+              (layer position at last layout (8,190))
>+            )
>+          )
>         )
>       )
>     )
>diff --git a/LayoutTests/scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt b/LayoutTests/scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt
>index 74da075953c82f3fefa47d71fabd592eb072adf3..312272dbfdea90a25c9544e80aca09d0ffb08451 100644
>--- a/LayoutTests/scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt
>+++ b/LayoutTests/scrollingcoordinator/scrolling-tree/fixed-inside-frame-expected.txt
>@@ -15,27 +15,31 @@
>   (max layout viewport origin (0,57))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 465 400)
>-      (contents size 465 1016)
>-      (requested scroll position 0 120)
>-      (requested scroll position represents programmatic scroll 1)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 0)
>-        (vertical scroll elasticity 0)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0)
>-        (has enabled vertical scrollbar 1))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,120) size 465x400)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,616))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>       (children 1
>-        (Fixed node
>-          (anchor edges: AnchorEdgeLeft AnchorEdgeTop)
>-          (viewport rect at last layout at (0,120) size 465x400)
>-          (layer position at last layout (10,130))
>+        (Frame scrolling node
>+          (scrollable area size 465 400)
>+          (contents size 465 1016)
>+          (requested scroll position 0 120)
>+          (requested scroll position represents programmatic scroll 1)
>+          (scrollable area parameters 
>+            (horizontal scroll elasticity 0)
>+            (vertical scroll elasticity 0)
>+            (horizontal scrollbar mode 0)
>+            (vertical scrollbar mode 0)
>+            (has enabled vertical scrollbar 1))
>+          (visual viewport enabled 1)
>+          (layout viewport at (0,120) size 465x400)
>+          (min layout viewport origin (0,0))
>+          (max layout viewport origin (0,616))
>+          (behavior for fixed 0)
>+          (children 1
>+            (Fixed node
>+              (anchor edges: AnchorEdgeLeft AnchorEdgeTop)
>+              (viewport rect at last layout at (0,120) size 465x400)
>+              (layer position at last layout (10,130))
>+            )
>+          )
>         )
>       )
>     )
>diff --git a/LayoutTests/scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt b/LayoutTests/scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt
>index 99fdd043a9722ae11ef9e381d07006a2faed0c88..38d2f710be3e73bbd1c70384568718a17ec945b0 100644
>--- a/LayoutTests/scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt
>+++ b/LayoutTests/scrollingcoordinator/scrolling-tree/scrolling-tree-includes-frame-expected.txt
>@@ -14,21 +14,25 @@
>   (max layout viewport origin (0,0))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 85 185)
>-      (contents size 308 416)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 0)
>-        (vertical scroll elasticity 0)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0)
>-        (has enabled horizontal scrollbar 1)
>-        (has enabled vertical scrollbar 1))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 85x185)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (223,231))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>+      (children 1
>+        (Frame scrolling node
>+          (scrollable area size 85 185)
>+          (contents size 308 416)
>+          (scrollable area parameters 
>+            (horizontal scroll elasticity 0)
>+            (vertical scroll elasticity 0)
>+            (horizontal scrollbar mode 0)
>+            (vertical scrollbar mode 0)
>+            (has enabled horizontal scrollbar 1)
>+            (has enabled vertical scrollbar 1))
>+          (visual viewport enabled 1)
>+          (layout viewport at (0,0) size 85x185)
>+          (min layout viewport origin (0,0))
>+          (max layout viewport origin (223,231))
>+          (behavior for fixed 0)
>+        )
>+      )
>     )
>   )
> )
>diff --git a/LayoutTests/scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt b/LayoutTests/scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt
>index cf7178d9ed1a65f92ce885e5380fbbadefe1d3c7..8323c1e0c1dbc314f1fd97dbcc9fcf3bcb5f0d6b 100644
>--- a/LayoutTests/scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt
>+++ b/LayoutTests/scrollingcoordinator/scrolling-tree/toggle-coordinated-frame-scrolling-expected.txt
>@@ -17,24 +17,11 @@ Scrolling tree on non-scrollable
>   (max layout viewport origin (0,40))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 585 500)
>-      (contents size 585 1024)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 0)
>-        (vertical scroll elasticity 0)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0)
>-        (has enabled vertical scrollbar 1))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 585x500)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,524))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>       (children 1
>         (Frame scrolling node
>-          (scrollable area size 485 400)
>-          (contents size 485 1024)
>+          (scrollable area size 585 500)
>+          (contents size 585 1024)
>           (scrollable area parameters 
>             (horizontal scroll elasticity 0)
>             (vertical scroll elasticity 0)
>@@ -42,10 +29,31 @@ Scrolling tree on non-scrollable
>             (vertical scrollbar mode 0)
>             (has enabled vertical scrollbar 1))
>           (visual viewport enabled 1)
>-          (layout viewport at (0,0) size 485x400)
>+          (layout viewport at (0,0) size 585x500)
>           (min layout viewport origin (0,0))
>-          (max layout viewport origin (0,624))
>+          (max layout viewport origin (0,524))
>           (behavior for fixed 0)
>+          (children 1
>+            (Frame hosting node
>+              (children 1
>+                (Frame scrolling node
>+                  (scrollable area size 485 400)
>+                  (contents size 485 1024)
>+                  (scrollable area parameters 
>+                    (horizontal scroll elasticity 0)
>+                    (vertical scroll elasticity 0)
>+                    (horizontal scrollbar mode 0)
>+                    (vertical scrollbar mode 0)
>+                    (has enabled vertical scrollbar 1))
>+                  (visual viewport enabled 1)
>+                  (layout viewport at (0,0) size 485x400)
>+                  (min layout viewport origin (0,0))
>+                  (max layout viewport origin (0,624))
>+                  (behavior for fixed 0)
>+                )
>+              )
>+            )
>+          )
>         )
>       )
>     )
>@@ -57,7 +65,7 @@ Scrolling tree on scrollable
> 
> (Frame scrolling node
>   (scrollable area size 785 600)
>-  (contents size 785 1421)
>+  (contents size 785 1541)
>   (scrollable area parameters 
>     (horizontal scroll elasticity 2)
>     (vertical scroll elasticity 2)
>@@ -67,37 +75,45 @@ Scrolling tree on scrollable
>   (visual viewport enabled 1)
>   (layout viewport at (0,0) size 785x600)
>   (min layout viewport origin (0,0))
>-  (max layout viewport origin (0,821))
>+  (max layout viewport origin (0,941))
>   (behavior for fixed 0)
>   (children 1
>-    (Frame scrolling node
>-      (scrollable area size 600 500)
>-      (contents size 600 500)
>-      (scrollable area parameters 
>-        (horizontal scroll elasticity 0)
>-        (vertical scroll elasticity 0)
>-        (horizontal scrollbar mode 0)
>-        (vertical scrollbar mode 0))
>-      (visual viewport enabled 1)
>-      (layout viewport at (0,0) size 600x500)
>-      (min layout viewport origin (0,0))
>-      (max layout viewport origin (0,0))
>-      (behavior for fixed 0)
>+    (Frame hosting node
>       (children 1
>         (Frame scrolling node
>-          (scrollable area size 485 400)
>-          (contents size 485 1024)
>+          (scrollable area size 600 500)
>+          (contents size 600 500)
>           (scrollable area parameters 
>             (horizontal scroll elasticity 0)
>             (vertical scroll elasticity 0)
>             (horizontal scrollbar mode 0)
>-            (vertical scrollbar mode 0)
>-            (has enabled vertical scrollbar 1))
>+            (vertical scrollbar mode 0))
>           (visual viewport enabled 1)
>-          (layout viewport at (0,0) size 485x400)
>+          (layout viewport at (0,0) size 600x500)
>           (min layout viewport origin (0,0))
>-          (max layout viewport origin (0,624))
>+          (max layout viewport origin (0,0))
>           (behavior for fixed 0)
>+          (children 1
>+            (Frame hosting node
>+              (children 1
>+                (Frame scrolling node
>+                  (scrollable area size 485 400)
>+                  (contents size 485 1024)
>+                  (scrollable area parameters 
>+                    (horizontal scroll elasticity 0)
>+                    (vertical scroll elasticity 0)
>+                    (horizontal scrollbar mode 0)
>+                    (vertical scrollbar mode 0)
>+                    (has enabled vertical scrollbar 1))
>+                  (visual viewport enabled 1)
>+                  (layout viewport at (0,0) size 485x400)
>+                  (min layout viewport origin (0,0))
>+                  (max layout viewport origin (0,624))
>+                  (behavior for fixed 0)
>+                )
>+              )
>+            )
>+          )
>         )
>       )
>     )

Flags:

koivisto: review+

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Attachments on bug 193879: 360265