Make squashing work with subpixel layout

Source/core/rendering/compositing/CompositedLayerMapping.h

 /*
  * Copyright (C) 2009, 2010, 2011 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 31 matching lines @@
 // A GraphicsLayerPaintInfo contains all the info needed to paint a partial subtree of RenderLayers into a GraphicsLayer.
 struct GraphicsLayerPaintInfo {
     RenderLayer* renderLayer;
 
     LayoutRect compositedBounds;
 
     // At first, the m_squashingLayer's bounds/location are not known. The value offsetFromSquashingCLM is
     // an intermediate offset for a squashed RenderLayer, described with respect to the CompositedLayerMapping's
     // owning layer that would eventually have the m_squashingLayer. Once the shared GraphicsLayer's bounds are
     // known, then we can trivially convert this offset to m_squashingLayer's space.
-    IntSize offsetFromSquashingCLM;
+    LayoutSize offsetFromSquashingCLM;
 
     // Offset describing where this squashed RenderLayer paints into the shared GraphicsLayer backing.
     IntSize offsetFromRenderer;
+    LayoutSize subpixelAccumulation;
 
     GraphicsLayerPaintingPhase paintingPhase;
 
     bool isBackgroundLayer;
 
     bool isEquivalentForSquashing(const GraphicsLayerPaintInfo& other)
     {
         // FIXME: offsetFromRenderer and compositedBounds should not be checked here, because
         // they are not yet fixed at the time this function is used.
         return renderLayer == other.renderLayer
@@ skipping 94 matching lines @@
     LayoutRect compositedBounds() const { return m_compositedBounds; }
     IntRect pixelSnappedCompositedBounds() const;
     void setCompositedBounds(const LayoutRect&);
     void updateCompositedBounds();
 
     void updateAfterWidgetResize();
     void positionOverflowControlsLayers(const IntSize& offsetFromRoot);
     bool hasUnpositionedOverflowControlsLayers() const;
 
     // Returns true if the assignment actually changed the assigned squashing layer.
-    bool updateSquashingLayerAssignment(RenderLayer*, IntSize offsetFromSquashingCLM, size_t nextSquashedLayerIndex);
+    bool updateSquashingLayerAssignment(RenderLayer*, LayoutSize offsetFromSquashingCLM, size_t nextSquashedLayerIndex);
     void removeRenderLayerFromSquashingGraphicsLayer(const RenderLayer*);
 
     void finishAccumulatingSquashingLayers(size_t nextSquashedLayerIndex);
     void updateRenderingContext();
     void updateShouldFlattenTransform();
 
     // GraphicsLayerClient interface
     virtual void notifyAnimationStarted(const GraphicsLayer*, double monotonicTime) OVERRIDE;
     virtual void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect& clip) OVERRIDE;
     virtual bool isTrackingRepaints() const OVERRIDE;
@@ skipping 180 matching lines @@
     bool m_requiresOwnBackingStoreForAncestorReasons : 1;
     bool m_canCompositeFilters : 1;
     bool m_backgroundLayerPaintsFixedRootBackground : 1;
     bool m_needToUpdateGeometry : 1;
     bool m_needToUpdateGeometryOfAllDecendants : 1;
 };
 
 } // namespace WebCore
 
 #endif // CompositedLayerMapping_h