Remove compositing trigger for will-change: top (and similar)

Source/core/rendering/style/RenderStyle.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 851 matching lines @@
     return false;
 }
 
 bool RenderStyle::hasWillChangeCompositingHint() const
 {
     for (size_t i = 0; i < rareNonInheritedData->m_willChange->m_properties.size(); ++i) {
         switch (rareNonInheritedData->m_willChange->m_properties[i]) {
         case CSSPropertyOpacity:
         case CSSPropertyTransform:
         case CSSPropertyWebkitTransform:
-        case CSSPropertyLeft:
-        case CSSPropertyTop:
-        case CSSPropertyRight:
-        case CSSPropertyBottom:
-        case CSSPropertyWebkitFilter:

[ajuma, 2014/05/07 20:16:43]

Are these removals still needed for correctness given the changes made to layer
creation logic in RenderBox and RenderTableRow? Since we now never specifically
create RenderLayers for will-change hints, there seems to be no harm leaving
these in (since they'll only cause already-existing layers to composite).

[abarth-chromium, 2014/05/07 20:19:59]

As I wrote in the change description, I think we should restore the system to
correctness and then possibly re-introduce these compositing triggers in the
future.  Currently they don't work.

             return true;
         default:
             break;
         }
     }
     return false;
 }
 
 inline bool requireTransformOrigin(const Vector<RefPtr<TransformOperation> >& transformOperations, RenderStyle::ApplyTransformOrigin applyOrigin)
 {
@@ skipping 765 matching lines @@
     // right
     radiiSum = radii.topRight().height() + radii.bottomRight().height();
     if (radiiSum > rect.height())
         factor = std::min(rect.height() / radiiSum, factor);
 
     ASSERT(factor <= 1);
     return factor;
 }
 
 } // namespace WebCore