Fix pixel snapping issues when layers become composited

Source/core/rendering/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 622 matching lines @@
 
         LayoutRect repaintRect = rect;
         repaintRect.moveBy(offset);
 
         compositedAncestor->repainter().setBackingNeedsRepaintInRect(repaintRect);
     }
 }
 
 // The bounds of the GraphicsLayer created for a compositing layer is the union of the bounds of all the descendant
 // RenderLayers that are rendered by the composited RenderLayer.
-IntRect RenderLayerCompositor::calculateCompositedBounds(const RenderLayer* layer, const RenderLayer* ancestorLayer) const
+LayoutRect RenderLayerCompositor::calculateCompositedBounds(const RenderLayer* layer, const RenderLayer* ancestorLayer) const
 {
     if (!canBeComposited(layer))
-        return IntRect();
+        return LayoutRect();
 
     RenderLayer::CalculateLayerBoundsFlags flags = RenderLayer::DefaultCalculateLayerBoundsFlags | RenderLayer::ExcludeHiddenDescendants | RenderLayer::DontConstrainForMask;
 #if HAVE(COMPOSITOR_FILTER_OUTSETS)
     // If the compositor computes its own filter outsets, don't include them in the composited bounds.
     if (!layer->paintsWithFilters())
         flags &= ~RenderLayer::IncludeLayerFilterOutsets;
 #endif
     return layer->calculateLayerBounds(ancestorLayer, 0, flags);
 }
 
@@ skipping 1787 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "Frame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore