Attachment 372980 Details for Bug 199253 – Patch

[patch] Patch

bug-199253-20190626180259.patch (text/plain), 47.24 KB, created by Simon Fraser (smfr) on 2019-06-26 18:03:00 PDT

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Creator: Simon Fraser (smfr)

Created: 2019-06-26 18:03:00 PDT

Size: 47.24 KB

patch

obsolete

>Subversion Revision: 246844
>diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
>index 6b0d732ad503c27f97c73862c70ead9a7f2c55a3..7ad5cf12c809c534afd51c8f4139c658692ca67a 100644
>--- a/Source/WebCore/ChangeLog
>+++ b/Source/WebCore/ChangeLog
>@@ -1,3 +1,52 @@
>+2019-06-26  Simon Fraser  <simon.fraser@apple.com>
>+
>+        [Async overflow scrolling] Fix missing or misplaced content inside overflow:scroll
>+        https://bugs.webkit.org/show_bug.cgi?id=199253
>+        rdar://problem/51855156, rdar://problem/51934514
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        This patch fixes a couple of related issues triggered by failing to composite layers inside non-stacking-context
>+        overflow scroll.
>+
>+        First, we relied on overlap testing to composite position:relative layers inside overflow:scroll, but this only
>+        worked when they came later in z-order, so didn't work for layers with negative z-index.
>+        RenderLayerCompositor::requiresCompositingForIndirectReason() was intended to trigger compositing in such cases,
>+        but it only did so for position:absolute inside stacking-context scroller, because
>+        isNonScrolledLayerInsideScrolledCompositedAncestor() tested ancestorMovedByScroller && !layerMovedByScroller.
>+
>+        I fixed this by sharing code between the three places that ask whether compositing crosses a containing-block
>+        boundary to call a single function, RenderLayerCompositor::layerScrollBehahaviorRelativeToCompositedAncestor(),
>+        that returns a ScrollPositioningBehavior. We now do compositing for both "moves" and "stationary" behaviors (but
>+        not "none"), ensuring that position:relative inside non-stacking scroller is always composited.
>+
>+        However, this would trigger compositing on layers that should be using backing sharing; if they were outside the
>+        visible part of the scroller, the overlap code would not trigger, but the
>+        "IndirectCompositingReason::OverflowScrollPositioning" code would. This is undesirable; any layer that can use
>+        backing sharing should, because that's fewer composited layers, so smaller layer trees and less backing store.
>+        To fix this, I moved the backing-sharing check before the overlap check in
>+        RenderLayerCompositor::computeCompositingRequirements().
>+
>+        The "layer.setHasCompositingDescendant(currentState.subtreeIsCompositing)" line was in the wrong place,
>+        triggering assertions on some content; "subtreeIsCompositing" only refers to child layers, so this bit needs to
>+        be set right after we've traversed the z-order lists.
>+
>+        Tests: compositing/scrolling/async-overflow-scrolling/hidden-relative-layer-content-in-scroller.html
>+               compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller.html
>+               compositing/scrolling/async-overflow-scrolling/negative-z-in-scroller.html
>+
>+        * rendering/RenderLayerCompositor.cpp:
>+        (WebCore::RenderLayerCompositor::computeCompositingRequirements):
>+        (WebCore::RenderLayerCompositor::traverseUnchangedSubtree):
>+        (WebCore::RenderLayerCompositor::requiresCompositingForIndirectReason const):
>+        (WebCore::isScrolledByOverflowScrollLayer):
>+        (WebCore::enclosingCompositedScrollingLayer):
>+        (WebCore::RenderLayerCompositor::layerScrollBehahaviorRelativeToCompositedAncestor):
>+        (WebCore::RenderLayerCompositor::computeCoordinatedPositioningForLayer const):
>+        (WebCore::isNonScrolledLayerInsideScrolledCompositedAncestor): Deleted.
>+        (WebCore::RenderLayerCompositor::layerContainingBlockCrossesCoordinatedScrollingBoundary): Deleted.
>+        * rendering/RenderLayerCompositor.h:
>+
> 2019-06-26  Antoine Quint  <graouts@apple.com>
> 
>         [Pointer Events] Respect pointer capture when dispatching mouse boundary events and updating :hover
>diff --git a/Source/WebCore/rendering/RenderLayerCompositor.cpp b/Source/WebCore/rendering/RenderLayerCompositor.cpp
>index d6becc3bc44e5af0e31e4ec376364b332473bc4c..ffa15da088edbcdaa7bea83e6a9ff6b0138a8dd7 100644
>--- a/Source/WebCore/rendering/RenderLayerCompositor.cpp
>+++ b/Source/WebCore/rendering/RenderLayerCompositor.cpp
>@@ -863,12 +863,21 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* ancestor
>     RequiresCompositingData queryData;
>     bool willBeComposited = layer.isComposited();
>     bool becameCompositedAfterDescendantTraversal = false;
>+    IndirectCompositingReason compositingReason = compositingState.subtreeIsCompositing ? IndirectCompositingReason::Stacking : IndirectCompositingReason::None;
> 
>     if (layer.needsPostLayoutCompositingUpdate() || compositingState.fullPaintOrderTraversalRequired || compositingState.descendantsRequireCompositingUpdate) {
>         layer.setIndirectCompositingReason(IndirectCompositingReason::None);
>         willBeComposited = needsToBeComposited(layer, queryData);
>     }
> 
>+    bool layerPaintsIntoProvidedBacking = false;
>+    if (!willBeComposited && compositingState.subtreeIsCompositing && backingSharingState.backingProviderCandidate() && canBeComposited(layer) && backingProviderLayerCanIncludeLayer(*backingSharingState.backingProviderCandidate(), layer)) {
>+        backingSharingState.appendSharingLayer(layer);
>+        LOG(Compositing, " layer %p can share with %p", &layer, backingSharingState.backingProviderCandidate());
>+        compositingReason = IndirectCompositingReason::None;
>+        layerPaintsIntoProvidedBacking = true;
>+    }
>+
>     compositingState.fullPaintOrderTraversalRequired |= layer.subsequentLayersNeedCompositingRequirementsTraversal();
> 
>     OverlapExtent layerExtent;
>@@ -880,22 +889,12 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* ancestor
>     bool respectTransforms = !layerExtent.hasTransformAnimation;
>     overlapMap.geometryMap().pushMappingsToAncestor(&layer, ancestorLayer, respectTransforms);
> 
>-    IndirectCompositingReason compositingReason = compositingState.subtreeIsCompositing ? IndirectCompositingReason::Stacking : IndirectCompositingReason::None;
>-    bool layerPaintsIntoProvidedBacking = false;
>-    bool didPushOverlapContainer = false;
>-
>     // If we know for sure the layer is going to be composited, don't bother looking it up in the overlap map
>-    if (!willBeComposited && !overlapMap.isEmpty() && compositingState.testingOverlap) {
>+    if (!willBeComposited && !layerPaintsIntoProvidedBacking && !overlapMap.isEmpty() && compositingState.testingOverlap) {
>         // If we're testing for overlap, we only need to composite if we overlap something that is already composited.
>-        if (layerOverlaps(overlapMap, layer, layerExtent)) {
>-            if (backingSharingState.backingProviderCandidate() && canBeComposited(layer) && backingProviderLayerCanIncludeLayer(*backingSharingState.backingProviderCandidate(), layer)) {
>-                backingSharingState.appendSharingLayer(layer);
>-                LOG(Compositing, " layer %p can share with %p", &layer, backingSharingState.backingProviderCandidate());
>-                compositingReason = IndirectCompositingReason::None;
>-                layerPaintsIntoProvidedBacking = true;
>-            } else
>-                compositingReason = IndirectCompositingReason::Overlap;
>-        } else
>+        if (layerOverlaps(overlapMap, layer, layerExtent))
>+            compositingReason = IndirectCompositingReason::Overlap;
>+        else
>             compositingReason = IndirectCompositingReason::None;
>     }
> 
>@@ -922,6 +921,7 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* ancestor
>     // a compositing layer among them, so start by inheriting the compositing
>     // ancestor with subtreeIsCompositing set to false.
>     CompositingState currentState = compositingState.stateForPaintOrderChildren(layer);
>+    bool didPushOverlapContainer = false;
> 
>     auto layerWillComposite = [&] {
>         // This layer is going to be composited, so children can safely ignore the fact that there's an
>@@ -993,6 +993,9 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* ancestor
>     for (auto* childLayer : layer.positiveZOrderLayers())
>         computeCompositingRequirements(&layer, *childLayer, overlapMap, currentState, backingSharingState, anyDescendantHas3DTransform);
> 
>+    // Set the flag to say that this layer has compositing children.
>+    layer.setHasCompositingDescendant(currentState.subtreeIsCompositing);
>+
>     // If we just entered compositing mode, the root will have become composited (as long as accelerated compositing is enabled).
>     if (layer.isRenderViewLayer()) {
>         if (usesCompositing() && m_hasAcceleratedCompositing)
>@@ -1022,9 +1025,6 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* ancestor
>         layer.reflectionLayer()->setIndirectCompositingReason(willBeComposited ? IndirectCompositingReason::Stacking : IndirectCompositingReason::None);
>     }
> 
>-    // Set the flag to say that this layer has compositing children.
>-    layer.setHasCompositingDescendant(currentState.subtreeIsCompositing);
>-
>     // setHasCompositingDescendant() may have changed the answer to needsToBeComposited() when clipping, so test that now.
>     bool isCompositedClippingLayer = canBeComposited(layer) && clipsCompositingDescendants(layer);
>     if (isCompositedClippingLayer & !willBeComposited)
>@@ -1150,7 +1150,7 @@ void RenderLayerCompositor::traverseUnchangedSubtree(RenderLayer* ancestorLayer,
>         if (currentState.subtreeIsCompositing)
>             ASSERT(layerIsComposited);
>     }
>-    
>+
>     for (auto* childLayer : layer.normalFlowLayers())
>         traverseUnchangedSubtree(&layer, *childLayer, overlapMap, currentState, backingSharingState, anyDescendantHas3DTransform);
> 
>@@ -2992,43 +2992,6 @@ bool RenderLayerCompositor::requiresCompositingForOverflowScrolling(const Render
>     return layer.hasCompositedScrollableOverflow();
> }
> 
>-static RenderLayer* enclosingCompositedScrollingLayer(const RenderLayer& layer, const RenderLayer& intermediateLayer, bool& sawIntermediateLayer)
>-{
>-    const auto* ancestorLayer = layer.parent();
>-    while (ancestorLayer) {
>-        if (ancestorLayer == &intermediateLayer)
>-            sawIntermediateLayer = true;
>-
>-        if (ancestorLayer->hasCompositedScrollableOverflow())
>-            return const_cast<RenderLayer*>(ancestorLayer);
>-
>-        ancestorLayer = ancestorLayer->parent();
>-    }
>-
>-    return nullptr;
>-}
>-
>-static bool isScrolledByOverflowScrollLayer(const RenderLayer& layer, const RenderLayer& overflowScrollLayer)
>-{
>-    bool scrolledByOverflowScroll = false;
>-    traverseAncestorLayers(layer, [&](const RenderLayer& ancestorLayer, bool inContainingBlockChain, bool) {
>-        if (&ancestorLayer == &overflowScrollLayer) {
>-            scrolledByOverflowScroll = inContainingBlockChain;
>-            return AncestorTraversal::Stop;
>-        }
>-        return AncestorTraversal::Continue;
>-    });
>-    return scrolledByOverflowScroll;
>-}
>-
>-static bool isNonScrolledLayerInsideScrolledCompositedAncestor(const RenderLayer& layer, const RenderLayer& compositedAncestor, const RenderLayer& scrollingAncestor)
>-{
>-    bool ancestorMovedByScroller = &compositedAncestor == &scrollingAncestor || isScrolledByOverflowScrollLayer(compositedAncestor, scrollingAncestor);
>-    bool layerMovedByScroller = isScrolledByOverflowScrollLayer(layer, scrollingAncestor);
>-
>-    return ancestorMovedByScroller && !layerMovedByScroller;
>-}
>-
> // FIXME: why doesn't this handle the clipping cases?
> bool RenderLayerCompositor::requiresCompositingForIndirectReason(const RenderLayer& layer, bool hasCompositedDescendants, bool has3DTransformedDescendants, bool paintsIntoProvidedBacking, IndirectCompositingReason& reason) const
> {
>@@ -3057,9 +3020,7 @@ bool RenderLayerCompositor::requiresCompositingForIndirectReason(const RenderLay
>     // If this layer scrolls independently from the layer that it would paint into, it needs to get composited.
>     if (!paintsIntoProvidedBacking && layer.hasCompositedScrollingAncestor()) {
>         auto* paintDestination = layer.paintOrderParent();
>-        bool paintDestinationIsScrolling = false;
>-        auto* scrollingAncestor = enclosingCompositedScrollingLayer(layer, *paintDestination, paintDestinationIsScrolling);
>-        if (isNonScrolledLayerInsideScrolledCompositedAncestor(layer, *paintDestination, *scrollingAncestor)) {
>+        if (paintDestination && layerScrollBehahaviorRelativeToCompositedAncestor(layer, *paintDestination) != ScrollPositioningBehavior::None) {
>             reason = IndirectCompositingReason::OverflowScrollPositioning;
>             return true;
>         }
>@@ -3164,19 +3125,54 @@ bool RenderLayerCompositor::useCoordinatedScrollingForLayer(const RenderLayer& l
>     return false;
> }
> 
>-bool RenderLayerCompositor::layerContainingBlockCrossesCoordinatedScrollingBoundary(const RenderLayer& layer, const RenderLayer& compositedAncestor)
>+static bool isScrolledByOverflowScrollLayer(const RenderLayer& layer, const RenderLayer& overflowScrollLayer)
> {
>+    bool scrolledByOverflowScroll = false;
>+    traverseAncestorLayers(layer, [&](const RenderLayer& ancestorLayer, bool inContainingBlockChain, bool) {
>+        if (&ancestorLayer == &overflowScrollLayer) {
>+            scrolledByOverflowScroll = inContainingBlockChain;
>+            return AncestorTraversal::Stop;
>+        }
>+        return AncestorTraversal::Continue;
>+    });
>+    return scrolledByOverflowScroll;
>+}
>+
>+static RenderLayer* enclosingCompositedScrollingLayer(const RenderLayer& layer, const RenderLayer& intermediateLayer, bool& sawIntermediateLayer)
>+{
>+    const auto* ancestorLayer = layer.parent();
>+    while (ancestorLayer) {
>+        if (ancestorLayer == &intermediateLayer)
>+            sawIntermediateLayer = true;
>+
>+        if (ancestorLayer->hasCompositedScrollableOverflow())
>+            return const_cast<RenderLayer*>(ancestorLayer);
>+
>+        ancestorLayer = ancestorLayer->parent();
>+    }
>+
>+    return nullptr;
>+}
>+
>+ScrollPositioningBehavior RenderLayerCompositor::layerScrollBehahaviorRelativeToCompositedAncestor(const RenderLayer& layer, const RenderLayer& compositedAncestor)
>+{
>+    if (!layer.hasCompositedScrollingAncestor())
>+        return ScrollPositioningBehavior::None;
>+
>     bool compositedAncestorIsInsideScroller = false;
>     auto* scrollingAncestor = enclosingCompositedScrollingLayer(layer, compositedAncestor, compositedAncestorIsInsideScroller);
>     if (!scrollingAncestor) {
>         ASSERT_NOT_REACHED(); // layer.hasCompositedScrollingAncestor() should guarantee we have one.
>-        return false;
>+        return ScrollPositioningBehavior::None;
>     }
>     
>-    if (!compositedAncestorIsInsideScroller)
>-        return false;
>+    bool ancestorMovedByScroller = &compositedAncestor == scrollingAncestor || (compositedAncestorIsInsideScroller && isScrolledByOverflowScrollLayer(compositedAncestor, *scrollingAncestor));
>+    bool layerMovedByScroller = isScrolledByOverflowScrollLayer(layer, *scrollingAncestor);
> 
>-    return isNonScrolledLayerInsideScrolledCompositedAncestor(layer, compositedAncestor, *scrollingAncestor);
>+    if (ancestorMovedByScroller == layerMovedByScroller)
>+        return ScrollPositioningBehavior::None;
>+
>+    return layerMovedByScroller ? ScrollPositioningBehavior::Moves : ScrollPositioningBehavior::Stationary;
> }
> 
> static void collectStationaryLayerRelatedOverflowNodes(const RenderLayer& layer, const RenderLayer&, Vector<ScrollingNodeID>& scrollingNodes)
>@@ -3227,27 +3223,7 @@ ScrollPositioningBehavior RenderLayerCompositor::computeCoordinatedPositioningFo
>         return ScrollPositioningBehavior::None;
>     }
> 
>-    bool compositedAncestorIsScrolling = false;
>-    auto* scrollingAncestor = enclosingCompositedScrollingLayer(layer, *compositedAncestor, compositedAncestorIsScrolling);
>-    if (!scrollingAncestor) {
>-        ASSERT_NOT_REACHED(); // layer.hasCompositedScrollingAncestor() should guarantee we have one.
>-        return ScrollPositioningBehavior::None;
>-    }
>-
>-    // There are two cases we have to deal with here:
>-    // 1. There's a composited overflow:scroll in the parent chain between the renderer and its containing block, and the layer's
>-    //    composited (z-order) ancestor is inside the scroller or is the scroller. In this case, we have to compensate for scroll position
>-    //    changes to make the positioned layer stay in the same place. This only applies to position:absolute or descendants of position:absolute.
>-    if (compositedAncestorIsScrolling && isNonScrolledLayerInsideScrolledCompositedAncestor(layer, *compositedAncestor, *scrollingAncestor))
>-        return ScrollPositioningBehavior::Stationary;
>-
>-    // 2. The layer's containing block is the overflow or inside the overflow:scroll, but its z-order ancestor is
>-    //    outside the overflow:scroll. In that case, we have to move the layer via the scrolling tree to make
>-    //    it move along with the overflow scrolling.
>-    if (!compositedAncestorIsScrolling && isScrolledByOverflowScrollLayer(layer, *scrollingAncestor))
>-        return ScrollPositioningBehavior::Moves;
>-
>-    return ScrollPositioningBehavior::None;
>+    return layerScrollBehahaviorRelativeToCompositedAncestor(layer, *compositedAncestor);
> }
> 
> static Vector<ScrollingNodeID> collectRelatedCoordinatedScrollingNodes(const RenderLayer& layer, ScrollPositioningBehavior positioningBehavior)
>diff --git a/Source/WebCore/rendering/RenderLayerCompositor.h b/Source/WebCore/rendering/RenderLayerCompositor.h
>index 21c06d97598ca945bebceade6c115e9a305bce61..ec35d7c9cb68805f43dbc5029873a94ca2fc3f8b 100644
>--- a/Source/WebCore/rendering/RenderLayerCompositor.h
>+++ b/Source/WebCore/rendering/RenderLayerCompositor.h
>@@ -497,7 +497,7 @@ private:
>     bool requiresCompositingForEditableImage(RenderLayerModelObject&) const;
>     bool requiresCompositingForIndirectReason(const RenderLayer&, bool hasCompositedDescendants, bool has3DTransformedDescendants, bool paintsIntoProvidedBacking, IndirectCompositingReason&) const;
> 
>-    static bool layerContainingBlockCrossesCoordinatedScrollingBoundary(const RenderLayer&, const RenderLayer& compositedAncestor);
>+    static ScrollPositioningBehavior layerScrollBehahaviorRelativeToCompositedAncestor(const RenderLayer&, const RenderLayer& compositedAncestor);
> 
>     static bool styleChangeMayAffectIndirectCompositingReasons(const RenderStyle& oldStyle, const RenderStyle& newStyle);
> 
>diff --git a/LayoutTests/ChangeLog b/LayoutTests/ChangeLog
>index f90083beaa805108847afb960a2622a06ec38f5e..90ca57c07a43a636280a0705b4ba76d0419a4d23 100644
>--- a/LayoutTests/ChangeLog
>+++ b/LayoutTests/ChangeLog
>@@ -1,3 +1,27 @@
>+2019-06-26  Simon Fraser  <simon.fraser@apple.com>
>+
>+        [Async overflow scrolling] Fix missing or misplaced content inside overflow:scroll
>+        https://bugs.webkit.org/show_bug.cgi?id=199253
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        * compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt:
>+        * compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt:
>+        * compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt:
>+        * compositing/rtl/rtl-scrolling-with-transformed-descendants-expected.txt:
>+        * compositing/scrolling/async-overflow-scrolling/hidden-relative-layer-content-in-scroller-expected.html: Added.
>+        * compositing/scrolling/async-overflow-scrolling/hidden-relative-layer-content-in-scroller.html: Added.
>+        * compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller-expected.txt: Added.
>+        * compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller.html: Added.
>+        * compositing/scrolling/async-overflow-scrolling/negative-z-in-scroller-expected.html: Added.
>+        * compositing/scrolling/async-overflow-scrolling/negative-z-in-scroller.html: Added.
>+        * compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt:
>+        * platform/ios-wk2/compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt:
>+        * platform/ios-wk2/compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt:
>+        * platform/ios-wk2/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller-expected.txt: Added.
>+        * platform/ios-wk2/compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt:
>+        * platform/ios/compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt:
>+
> 2019-06-26  Antoine Quint  <graouts@apple.com>
> 
>         [Pointer Events] Respect pointer capture when dispatching mouse boundary events and updating :hover
>diff --git a/LayoutTests/compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt b/LayoutTests/compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt
>index 65c4c45d7d92ca53d29f0a33af231ef922fd320c..42c36561cda62df06707c82361a6bca72e2f4c98 100644
>--- a/LayoutTests/compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt
>+++ b/LayoutTests/compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt
>@@ -27,7 +27,8 @@ middlebottom
>           (children 1
>             (GraphicsLayer
>               (offsetFromRenderer width=0 height=100)
>-              (bounds 149.00 200.00)
>+              (bounds 149.00 2086.00)
>+              (usingTiledLayer 1)
>               (drawsContent 1)
>             )
>           )
>diff --git a/LayoutTests/compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt b/LayoutTests/compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt
>index 49db9d9f4417411cc2fad73c1f9b25bef730424e..4f46c8367761482c74b57b38498958bb6b3cec30 100644
>--- a/LayoutTests/compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt
>+++ b/LayoutTests/compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt
>@@ -5,7 +5,7 @@
>     (GraphicsLayer
>       (bounds 800.00 600.00)
>       (contentsOpaque 1)
>-      (children 5
>+      (children 6
>         (GraphicsLayer
>           (position 8.00 8.00)
>           (bounds 302.00 302.00)
>@@ -69,6 +69,17 @@
>             )
>           )
>         )
>+        (GraphicsLayer
>+          (position 9.00 9.00)
>+          (bounds 285.00 300.00)
>+          (children 1
>+            (GraphicsLayer
>+              (position 40.00 380.00)
>+              (bounds 100.00 100.00)
>+              (contentsOpaque 1)
>+            )
>+          )
>+        )
>       )
>     )
>   )
>diff --git a/LayoutTests/compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt b/LayoutTests/compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt
>index cd78b437d266fa48e1124c310fa0b1cb621ca639..fd1bdf3f9b80bd9e72fc5d54560a23317320534b 100644
>--- a/LayoutTests/compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt
>+++ b/LayoutTests/compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt
>@@ -5,56 +5,88 @@
>     (GraphicsLayer
>       (bounds 800.00 600.00)
>       (contentsOpaque 1)
>-      (children 4
>+      (children 1
>         (GraphicsLayer
>-          (position 8.00 8.00)
>-          (bounds 302.00 302.00)
>+          (bounds 800.00 600.00)
>           (drawsContent 1)
>-          (children 1
>+          (children 7
>             (GraphicsLayer
>-              (offsetFromRenderer width=1 height=1)
>-              (position 1.00 1.00)
>+              (position 9.00 9.00)
>               (bounds 285.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 40.00 140.00)
>+                  (bounds 100.00 100.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>+            )
>+            (GraphicsLayer
>+              (bounds 800.00 600.00)
>+              (drawsContent 1)
>+            )
>+            (GraphicsLayer
>+              (position 8.00 8.00)
>+              (bounds 302.00 302.00)
>+              (drawsContent 1)
>               (children 1
>                 (GraphicsLayer
>                   (offsetFromRenderer width=1 height=1)
>-                  (anchor 0.00 0.00)
>-                  (bounds 285.00 500.00)
>+                  (position 1.00 1.00)
>+                  (bounds 285.00 300.00)
>+                  (children 1
>+                    (GraphicsLayer
>+                      (offsetFromRenderer width=1 height=1)
>+                      (anchor 0.00 0.00)
>+                      (bounds 285.00 500.00)
>+                    )
>+                  )
>                 )
>               )
>             )
>-          )
>-        )
>-        (GraphicsLayer
>-          (position 9.00 9.00)
>-          (bounds 285.00 300.00)
>-          (children 1
>             (GraphicsLayer
>-              (position 10.00 10.00)
>-              (bounds 50.00 200.00)
>-              (contentsOpaque 1)
>+              (position 9.00 9.00)
>+              (bounds 285.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 10.00 10.00)
>+                  (bounds 50.00 200.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>             )
>-          )
>-        )
>-        (GraphicsLayer
>-          (position 9.00 9.00)
>-          (bounds 285.00 300.00)
>-          (children 1
>             (GraphicsLayer
>-              (position 40.00 20.00)
>-              (bounds 100.00 100.00)
>-              (contentsOpaque 1)
>+              (position 9.00 9.00)
>+              (bounds 285.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 40.00 20.00)
>+                  (bounds 100.00 100.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>             )
>-          )
>-        )
>-        (GraphicsLayer
>-          (position 9.00 9.00)
>-          (bounds 285.00 300.00)
>-          (children 1
>             (GraphicsLayer
>-              (position 40.00 260.00)
>-              (bounds 100.00 100.00)
>-              (contentsOpaque 1)
>+              (position 9.00 9.00)
>+              (bounds 285.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 40.00 260.00)
>+                  (bounds 100.00 100.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>+            )
>+            (GraphicsLayer
>+              (position 9.00 9.00)
>+              (bounds 285.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 40.00 380.00)
>+                  (bounds 100.00 100.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>             )
>           )
>         )
>diff --git a/LayoutTests/compositing/rtl/rtl-scrolling-with-transformed-descendants-expected.txt b/LayoutTests/compositing/rtl/rtl-scrolling-with-transformed-descendants-expected.txt
>index c446161a6bd66ba301ebbc742827fb3e511ee624..3e4da39acdfc00fb7c5bbe623a26ac7cc9803831 100644
>--- a/LayoutTests/compositing/rtl/rtl-scrolling-with-transformed-descendants-expected.txt
>+++ b/LayoutTests/compositing/rtl/rtl-scrolling-with-transformed-descendants-expected.txt
>@@ -7,7 +7,7 @@
>     (GraphicsLayer
>       (bounds 800.00 600.00)
>       (contentsOpaque 1)
>-      (children 3
>+      (children 5
>         (GraphicsLayer
>           (position 8.00 8.00)
>           (bounds 404.00 223.00)
>@@ -58,6 +58,31 @@
>             )
>           )
>         )
>+        (GraphicsLayer
>+          (position 10.00 10.00)
>+          (bounds origin 366.00 0.00)
>+          (bounds 400.00 204.00)
>+          (clips 1)
>+          (children 1
>+            (GraphicsLayer
>+              (position 154.00 0.00)
>+              (bounds 150.00 200.00)
>+              (contentsOpaque 1)
>+            )
>+          )
>+        )
>+        (GraphicsLayer
>+          (position 10.00 10.00)
>+          (bounds origin 366.00 0.00)
>+          (bounds 400.00 204.00)
>+          (clips 1)
>+          (children 1
>+            (GraphicsLayer
>+              (bounds 150.00 200.00)
>+              (contentsOpaque 1)
>+            )
>+          )
>+        )
>       )
>     )
>   )
>diff --git a/LayoutTests/compositing/scrolling/async-overflow-scrolling/hidden-relative-layer-content-in-scroller-expected.html b/LayoutTests/compositing/scrolling/async-overflow-scrolling/hidden-relative-layer-content-in-scroller-expected.html
>new file mode 100644
>index 0000000000000000000000000000000000000000..873e45cf1b6bdb6901ed3ddab7df42fc2e27c15e
>--- /dev/null
>+++ b/LayoutTests/compositing/scrolling/async-overflow-scrolling/hidden-relative-layer-content-in-scroller-expected.html
>@@ -0,0 +1,71 @@
>+<!DOCTYPE html>
>+<html>
>+<head>
>+    <style>
>+        .page-scroller {
>+            height: 500px;
>+            width: 500px;
>+            overflow: hidden;
>+            border: 1px solid black;
>+        }
>+
>+        .relative {
>+            position: relative;
>+            height: 500px;
>+            width: 100%;
>+        }
>+                
>+        .absolute {
>+            position: absolute;
>+            z-index: 1;
>+            top: 20px;
>+            left: 20px;
>+            right: 20px;
>+            bottom: 20px;
>+        }
>+
>+        .scroller {
>+            overflow-y: auto;
>+            width: 100%;
>+            height: 100%;
>+            background: white;
>+            border: 1px solid black;
>+        }
>+
>+        .relative-content {
>+            position: relative;
>+            width: 100%;
>+            height: 600px;
>+            background-color: green;
>+        }
>+        .content-sizer {
>+            width: 100%;
>+            height: 750px;
>+            background-color: silver;
>+        }
>+        
>+        .scrollbars-hider {
>+            position: absolute;
>+            z-index: 2;
>+            top: 6px;
>+            left: 458px;
>+            width: 56px;
>+            height: 510px;
>+            background-color: gray;
>+        }
>+    </style>
>+</head>
>+<body>
>+    <div class="page-scroller">
>+        <div class="relative">
>+            <div class="content-sizer"></div>
>+            <div class="absolute">
>+                <div class="scroller">
>+                    <div class="relative-content"></div>
>+                </div>
>+            </div>
>+        </div>
>+    </div>
>+    <div class="scrollbars-hider"></div>
>+</body>
>+</html>
>diff --git a/LayoutTests/compositing/scrolling/async-overflow-scrolling/hidden-relative-layer-content-in-scroller.html b/LayoutTests/compositing/scrolling/async-overflow-scrolling/hidden-relative-layer-content-in-scroller.html
>new file mode 100644
>index 0000000000000000000000000000000000000000..8cf03b5df51cf4233c088464a71c4eb1816017cf
>--- /dev/null
>+++ b/LayoutTests/compositing/scrolling/async-overflow-scrolling/hidden-relative-layer-content-in-scroller.html
>@@ -0,0 +1,72 @@
>+<!DOCTYPE html>
>+<html>
>+<head>
>+    <style>
>+        .page-scroller {
>+            height: 500px;
>+            width: 500px;
>+            overflow-y:auto;
>+            overflow-x: hidden;
>+            border: 1px solid black;
>+        }
>+
>+        .relative {
>+            position: relative;
>+            height: 500px;
>+            width: 100%;
>+        }
>+                
>+        .absolute {
>+            position: absolute;
>+            z-index: 1;
>+            top: 20px;
>+            left: 20px;
>+            right: 20px;
>+            bottom: 20px;
>+        }
>+
>+        .scroller {
>+            overflow-y: auto;
>+            width: 100%;
>+            height: 100%;
>+            background: white;
>+            border: 1px solid black;
>+        }
>+
>+        .relative-content {
>+            position: relative;
>+            width: 100%;
>+            height: 600px;
>+            background-color: green;
>+        }
>+        .content-sizer {
>+            width: 100%;
>+            height: 750px;
>+            background-color: silver;
>+        }
>+        
>+        .scrollbars-hider {
>+            position: absolute;
>+            z-index: 2;
>+            top: 6px;
>+            left: 458px;
>+            width: 56px;
>+            height: 510px;
>+            background-color: gray;
>+        }
>+    </style>
>+</head>
>+<body>
>+    <div class="page-scroller">
>+        <div class="relative">
>+            <div class="content-sizer"></div>
>+            <div class="absolute">
>+                <div class="scroller">
>+                    <div class="relative-content"></div>
>+                </div>
>+            </div>
>+        </div>
>+    </div>
>+    <div class="scrollbars-hider"></div>
>+</body>
>+</html>
>diff --git a/LayoutTests/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller-expected.txt b/LayoutTests/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller-expected.txt
>new file mode 100644
>index 0000000000000000000000000000000000000000..79e3419265c2899643cc619b14d5d251766ab23e
>--- /dev/null
>+++ b/LayoutTests/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller-expected.txt
>@@ -0,0 +1,35 @@
>+(GraphicsLayer
>+  (anchor 0.00 0.00)
>+  (bounds 800.00 600.00)
>+  (clips 1)
>+  (children 1
>+    (GraphicsLayer
>+      (bounds 800.00 600.00)
>+      (contentsOpaque 1)
>+      (children 1
>+        (GraphicsLayer
>+          (position 8.00 8.00)
>+          (bounds 302.00 302.00)
>+          (drawsContent 1)
>+          (children 1
>+            (GraphicsLayer
>+              (offsetFromRenderer width=1 height=1)
>+              (position 1.00 1.00)
>+              (bounds 285.00 300.00)
>+              (clips 1)
>+              (children 1
>+                (GraphicsLayer
>+                  (offsetFromRenderer width=1 height=1)
>+                  (anchor 0.00 0.00)
>+                  (bounds 285.00 1240.00)
>+                  (drawsContent 1)
>+                )
>+              )
>+            )
>+          )
>+        )
>+      )
>+    )
>+  )
>+)
>+
>diff --git a/LayoutTests/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller.html b/LayoutTests/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller.html
>new file mode 100644
>index 0000000000000000000000000000000000000000..8f9e78335dfdd9f6902861dba2a336db5131fc4d
>--- /dev/null
>+++ b/LayoutTests/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller.html
>@@ -0,0 +1,46 @@
>+<!DOCTYPE html> 
>+<html>
>+<head>
>+    <style>
>+		#scroller {
>+			position: relative;
>+			overflow-y: scroll;
>+			width: 300px;
>+			height: 300px;
>+			border: 1px solid black;
>+		}
>+
>+		.negative {
>+			position: relative;
>+			z-index: -1;
>+			margin: 20px;
>+		    width: 200px;
>+		    height: 200px;
>+		    background-color: green;
>+		}
>+
>+        .spacer {
>+            height: 1000px;
>+            width: 10px;
>+            background-color: silver;
>+        }
>+    </style>
>+    <script>
>+        if (window.testRunner)
>+            testRunner.dumpAsText();
>+
>+        window.addEventListener('load', () => {
>+            if (window.internals)
>+                document.getElementById('layers').innerText = window.internals.layerTreeAsText(document, internals.LAYER_TREE_INCLUDES_CLIPPING);
>+        }, false);
>+    </script>
>+</head>
>+<body>
>+	<div id="scroller">
>+        <div class="negative box"></div>
>+        <div class="spacer"></div>
>+	</div>
>+<pre id="layers"></pre>
>+</body>
>+</html>
>+
>diff --git a/LayoutTests/compositing/scrolling/async-overflow-scrolling/negative-z-in-scroller-expected.html b/LayoutTests/compositing/scrolling/async-overflow-scrolling/negative-z-in-scroller-expected.html
>new file mode 100644
>index 0000000000000000000000000000000000000000..3f84332e959d855277d4581fa7d3c04a4795e3dd
>--- /dev/null
>+++ b/LayoutTests/compositing/scrolling/async-overflow-scrolling/negative-z-in-scroller-expected.html
>@@ -0,0 +1,48 @@
>+<!DOCTYPE html> 
>+<html>
>+<head>
>+    <style>
>+		#scroller {
>+			position: relative;
>+			overflow-y: scroll;
>+			width: 300px;
>+			height: 300px;
>+			border: 1px solid black;
>+		}
>+
>+		.negative {
>+			position: relative;
>+			z-index: 1;
>+			margin: 20px;
>+		    width: 200px;
>+		    height: 200px;
>+		    background-color: green;
>+		}
>+
>+        .spacer {
>+            height: 1000px;
>+            width: 10px;
>+            background-color: silver;
>+        }
>+    </style>
>+    <script>
>+        if (window.testRunner)
>+            testRunner.waitUntilDone();
>+
>+        window.addEventListener('load', () => {
>+            setTimeout(() => {
>+                scroller.scrollTo(0, 300);
>+                if (window.testRunner)
>+                    testRunner.notifyDone();
>+            }, 0)
>+        }, false);
>+    </script>
>+</head>
>+<body>
>+	<div id="scroller">
>+        <div class="negative box"></div>
>+        <div class="spacer"></div>
>+	</div>
>+</body>
>+</html>
>+
>diff --git a/LayoutTests/compositing/scrolling/async-overflow-scrolling/negative-z-in-scroller.html b/LayoutTests/compositing/scrolling/async-overflow-scrolling/negative-z-in-scroller.html
>new file mode 100644
>index 0000000000000000000000000000000000000000..dae9c540bf813e0422303acc187d8b45a3131d53
>--- /dev/null
>+++ b/LayoutTests/compositing/scrolling/async-overflow-scrolling/negative-z-in-scroller.html
>@@ -0,0 +1,48 @@
>+<!DOCTYPE html> 
>+<html>
>+<head>
>+    <style>
>+		#scroller {
>+			position: relative;
>+			overflow-y: scroll;
>+			width: 300px;
>+			height: 300px;
>+			border: 1px solid black;
>+		}
>+
>+		.negative {
>+			position: relative;
>+			z-index: -1;
>+			margin: 20px;
>+		    width: 200px;
>+		    height: 200px;
>+		    background-color: green;
>+		}
>+
>+        .spacer {
>+            height: 1000px;
>+            width: 10px;
>+            background-color: silver;
>+        }
>+    </style>
>+    <script>
>+        if (window.testRunner)
>+            testRunner.waitUntilDone();
>+
>+        window.addEventListener('load', () => {
>+            setTimeout(() => {
>+                scroller.scrollTo(0, 300);
>+                if (window.testRunner)
>+                    testRunner.notifyDone();
>+            }, 0)
>+        }, false);
>+    </script>
>+</head>
>+<body>
>+	<div id="scroller">
>+        <div class="negative box"></div>
>+        <div class="spacer"></div>
>+	</div>
>+</body>
>+</html>
>+
>diff --git a/LayoutTests/compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt b/LayoutTests/compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt
>index 5c321929e2f8c3cfbaccfb66d154ccca47a3f32e..05a3181a95a21706454e047282bce0cdecc3a61e 100644
>--- a/LayoutTests/compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt
>+++ b/LayoutTests/compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt
>@@ -28,11 +28,6 @@
>                       (bounds 140.00 140.00)
>                       (contentsOpaque 1)
>                       (drawsContent 1)
>-                      (children 1
>-                        (GraphicsLayer
>-                          (bounds 140.00 140.00)
>-                        )
>-                      )
>                     )
>                   )
>                 )
>diff --git a/LayoutTests/platform/ios-wk2/compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt b/LayoutTests/platform/ios-wk2/compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt
>index 97afdb5ebf4f860d0bc64e557cef3246eebad73f..5ef9bda1cb0207239e495f5b20d861253670588e 100644
>--- a/LayoutTests/platform/ios-wk2/compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/compositing/layer-creation/clipping-scope/overlap-constrained-inside-scroller-expected.txt
>@@ -5,7 +5,7 @@
>     (GraphicsLayer
>       (bounds 800.00 600.00)
>       (contentsOpaque 1)
>-      (children 5
>+      (children 6
>         (GraphicsLayer
>           (position 8.00 8.00)
>           (bounds 302.00 302.00)
>@@ -69,6 +69,17 @@
>             )
>           )
>         )
>+        (GraphicsLayer
>+          (position 9.00 9.00)
>+          (bounds 300.00 300.00)
>+          (children 1
>+            (GraphicsLayer
>+              (position 40.00 380.00)
>+              (bounds 100.00 100.00)
>+              (contentsOpaque 1)
>+            )
>+          )
>+        )
>       )
>     )
>   )
>diff --git a/LayoutTests/platform/ios-wk2/compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt b/LayoutTests/platform/ios-wk2/compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt
>index 0d9b8faf56a3d72263d0684d017aaab59acc244f..b9656b6921ef4d80982eb6e713b2683786f24ac3 100644
>--- a/LayoutTests/platform/ios-wk2/compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/compositing/layer-creation/clipping-scope/scroller-with-negative-z-children-expected.txt
>@@ -5,56 +5,88 @@
>     (GraphicsLayer
>       (bounds 800.00 600.00)
>       (contentsOpaque 1)
>-      (children 4
>+      (children 1
>         (GraphicsLayer
>-          (position 8.00 8.00)
>-          (bounds 302.00 302.00)
>+          (bounds 800.00 600.00)
>           (drawsContent 1)
>-          (children 1
>+          (children 7
>             (GraphicsLayer
>-              (offsetFromRenderer width=1 height=1)
>-              (position 1.00 1.00)
>+              (position 9.00 9.00)
>               (bounds 300.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 40.00 140.00)
>+                  (bounds 100.00 100.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>+            )
>+            (GraphicsLayer
>+              (bounds 800.00 600.00)
>+              (drawsContent 1)
>+            )
>+            (GraphicsLayer
>+              (position 8.00 8.00)
>+              (bounds 302.00 302.00)
>+              (drawsContent 1)
>               (children 1
>                 (GraphicsLayer
>                   (offsetFromRenderer width=1 height=1)
>-                  (anchor 0.00 0.00)
>-                  (bounds 300.00 500.00)
>+                  (position 1.00 1.00)
>+                  (bounds 300.00 300.00)
>+                  (children 1
>+                    (GraphicsLayer
>+                      (offsetFromRenderer width=1 height=1)
>+                      (anchor 0.00 0.00)
>+                      (bounds 300.00 500.00)
>+                    )
>+                  )
>                 )
>               )
>             )
>-          )
>-        )
>-        (GraphicsLayer
>-          (position 9.00 9.00)
>-          (bounds 300.00 300.00)
>-          (children 1
>             (GraphicsLayer
>-              (position 10.00 10.00)
>-              (bounds 50.00 200.00)
>-              (contentsOpaque 1)
>+              (position 9.00 9.00)
>+              (bounds 300.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 10.00 10.00)
>+                  (bounds 50.00 200.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>             )
>-          )
>-        )
>-        (GraphicsLayer
>-          (position 9.00 9.00)
>-          (bounds 300.00 300.00)
>-          (children 1
>             (GraphicsLayer
>-              (position 40.00 20.00)
>-              (bounds 100.00 100.00)
>-              (contentsOpaque 1)
>+              (position 9.00 9.00)
>+              (bounds 300.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 40.00 20.00)
>+                  (bounds 100.00 100.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>             )
>-          )
>-        )
>-        (GraphicsLayer
>-          (position 9.00 9.00)
>-          (bounds 300.00 300.00)
>-          (children 1
>             (GraphicsLayer
>-              (position 40.00 260.00)
>-              (bounds 100.00 100.00)
>-              (contentsOpaque 1)
>+              (position 9.00 9.00)
>+              (bounds 300.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 40.00 260.00)
>+                  (bounds 100.00 100.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>+            )
>+            (GraphicsLayer
>+              (position 9.00 9.00)
>+              (bounds 300.00 300.00)
>+              (children 1
>+                (GraphicsLayer
>+                  (position 40.00 380.00)
>+                  (bounds 100.00 100.00)
>+                  (contentsOpaque 1)
>+                )
>+              )
>             )
>           )
>         )
>diff --git a/LayoutTests/platform/ios-wk2/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller-expected.txt b/LayoutTests/platform/ios-wk2/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller-expected.txt
>new file mode 100644
>index 0000000000000000000000000000000000000000..85ccdaf48eb6f3dff378e7bd2e5f830767f22747
>--- /dev/null
>+++ b/LayoutTests/platform/ios-wk2/compositing/scrolling/async-overflow-scrolling/layer-for-negative-z-in-scroller-expected.txt
>@@ -0,0 +1,35 @@
>+(GraphicsLayer
>+  (anchor 0.00 0.00)
>+  (bounds 800.00 600.00)
>+  (clips 1)
>+  (children 1
>+    (GraphicsLayer
>+      (bounds 800.00 600.00)
>+      (contentsOpaque 1)
>+      (children 1
>+        (GraphicsLayer
>+          (position 8.00 8.00)
>+          (bounds 302.00 302.00)
>+          (drawsContent 1)
>+          (children 1
>+            (GraphicsLayer
>+              (offsetFromRenderer width=1 height=1)
>+              (position 1.00 1.00)
>+              (bounds 300.00 300.00)
>+              (clips 1)
>+              (children 1
>+                (GraphicsLayer
>+                  (offsetFromRenderer width=1 height=1)
>+                  (anchor 0.00 0.00)
>+                  (bounds 300.00 1240.00)
>+                  (drawsContent 1)
>+                )
>+              )
>+            )
>+          )
>+        )
>+      )
>+    )
>+  )
>+)
>+
>diff --git a/LayoutTests/platform/ios-wk2/compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt b/LayoutTests/platform/ios-wk2/compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt
>index 7647e2e13a5f7b79a36e80b2503bcf6a42efa509..8d96467a72d47f5fcd07ab92480a21f6e320e6fe 100644
>--- a/LayoutTests/platform/ios-wk2/compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt
>+++ b/LayoutTests/platform/ios-wk2/compositing/shared-backing/overflow-scroll/nested-absolute-with-clipping-in-stacking-overflow-expected.txt
>@@ -28,11 +28,6 @@
>                       (bounds 140.00 140.00)
>                       (contentsOpaque 1)
>                       (drawsContent 1)
>-                      (children 1
>-                        (GraphicsLayer
>-                          (bounds 140.00 140.00)
>-                        )
>-                      )
>                     )
>                   )
>                 )
>diff --git a/LayoutTests/platform/ios/compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt b/LayoutTests/platform/ios/compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt
>index 1648a491c516ddd1d9a23baad9b2f6d5da8a6f87..fd6996d8e8ee2033cf4a3eb4edc5977f55af15b7 100644
>--- a/LayoutTests/platform/ios/compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt
>+++ b/LayoutTests/platform/ios/compositing/geometry/limit-layer-bounds-clipping-ancestor-expected.txt
>@@ -27,7 +27,8 @@ middlebottom
>           (children 1
>             (GraphicsLayer
>               (offsetFromRenderer width=0 height=100)
>-              (bounds 149.00 200.00)
>+              (bounds 149.00 2086.00)
>+              (usingTiledLayer 1)
>               (drawsContent 1)
>             )
>           )

Flags:

zalan: review+

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Attachments on bug 199253: 372980