Bug 167185

Summary: Internals should not reset RuntimeEnabledFeatures, they should be set consistently by TestRunners -- Tests are very confused about RuntimeEnabledFeatures. DumpRenderTree: - DumpRenderTree.mm (Mac): resetWebPreferencesToConsistentValues sets a number of WebPreferences APIs that toggle RuntimeEnabledFeatures - DumpRenderTree.cpp (Win): resetWebPreferencesToConsistentValues sets a number of WebPreferences APIs that toggle RuntimeEnabledFeatures WebKitTestRunner: - TestController.cpp (All): TestController::resetPreferencesToConsistentValues toggles RuntimeEnabledFeatures (WKPreferencesEnableAllExperimentalFeatures) WebCoreTestSupport: - Internals.cpp (All): Internals::Internals resets RuntimeEnabledFeatures without taking into account DumpRenderTree/WebKitTestRunner non-defaults - Internals.cpp (All): Various APIs toggle RuntimeEnabledFeatures while a test is running Internals stomps on the Test Runners values, but only sometimes. This results in very confusing results where sometimes a Runtime feature is enabled and sometimes disabled. I'm going to propose some guidelines: 1. DumpRenderTree / WebKitTestRunner should configure settings appropriately - They already do between tests with the appropriately named resetPreferencesToConsistentValues. - This allows our tests to have things like experimental features enabled for tests even if they are not enabled by default for ports. - WebKit2 currently does this automatically. - WebKit1 developers / reviewers will need to remember to follow the pattern. 2. Internals should not reset RuntimeEnabledFeatures - The values in RuntimeEnabledFeatures::reset may not match the defaults set by TestRunners. - Internals doesn't know what features the TestRunners will want. 3. Internal toggle APIs can exist - If a test really wants to enable/disable a runtime feature this is a quick and easy way to do it. This should be, and is, super rare. - Tests shouldn't need to remember to restore the default value. The test runners should already be doing that, see (1). Possible issues: - There may be a RuntimeEnabled feature for which there is no WebPreferences API to toggle it. - Seems in these cases we should just add an API.