Don't include scroll offset in offsetFromLayoutObject for scrolling contents layers.

third_party/WebKit/Source/core/layout/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 110 matching lines @@
     bool hasChildTransformLayer() const { return m_childTransformLayer.get(); }
     GraphicsLayer* childTransformLayer() const { return m_childTransformLayer.get(); }
 
     GraphicsLayer* squashingContainmentLayer() const { return m_squashingContainmentLayer.get(); }
     GraphicsLayer* squashingLayer() const { return m_squashingLayer.get(); }
 
     void setSquashingContentsNeedDisplay();
     void setContentsNeedDisplay();
     // LayoutRect is in the coordinate space of the layer's layout object.
     void setContentsNeedDisplayInRect(const LayoutRect&, PaintInvalidationReason, const DisplayItemClient&);
+    // Invalidates just scrolling content layers.
+    void setScrollingContentsNeedDisplayInRect(const LayoutRect&, PaintInvalidationReason, const DisplayItemClient&);
 
     // This is called only if we are tracking paint invalidation for testing, or ENABLE(ASSERT)
     // for error checking and debugging.
     void displayItemClientWasInvalidated(const DisplayItemClient&, PaintInvalidationReason);
 
     // Notification from the layoutObject that its content changed.
     void contentChanged(ContentChangeType);
 
     LayoutRect compositedBounds() const { return m_compositedBounds; }
     IntRect pixelSnappedCompositedBounds() const;
@@ skipping 68 matching lines @@
     LayoutPoint squashingOffsetFromTransformedAncestor()
     {
         return m_squashingLayerOffsetFromTransformedAncestor;
     }
 
     // If there is a squashed layer painting into this CLM that is an ancestor of the given LayoutObject, return it. Otherwise return nullptr.
     const GraphicsLayerPaintInfo* containingSquashedLayer(const LayoutObject*, unsigned maxSquashedLayerIndex);
 
     void updateScrollingBlockSelection();
 
+    void adjustForCompositedScrolling(const GraphicsLayer*, IntSize& offset) const;
+
 private:
     IntRect recomputeInterestRect(const GraphicsLayer*) const;
     static bool interestRectChangedEnoughToRepaint(const IntRect& previousInterestRect, const IntRect& newInterestRect, const IntSize& layerSize);
 
     static const GraphicsLayerPaintInfo* containingSquashedLayer(const LayoutObject*,  const Vector<GraphicsLayerPaintInfo>& layers, unsigned maxSquashedLayerIndex);
 
     // Paints the scrollbar part associated with the given graphics layer into the given context.
     void paintScrollableArea(const GraphicsLayer*, GraphicsContext&, const IntRect& interestRect) const;
     // Returns whether the given layer is part of the scrollable area, if any, associated with this mapping.
     bool isScrollableAreaLayer(const GraphicsLayer*) const;
@@ skipping 204 matching lines @@
     // Stacking children of a squashed layer receive graphics layers that are parented to the compositd ancestor of the
     // squashed layer (i.e. nearest enclosing composited layer that is not squashed).
     OwnPtr<GraphicsLayer> m_squashingContainmentLayer; // Only used if any squashed layers exist and m_squashingContainmentLayer is not present, to contain the squashed layers as siblings to the rest of the GraphicsLayer tree chunk.
     OwnPtr<GraphicsLayer> m_squashingLayer; // Only used if any squashed layers exist, this is the backing that squashed layers paint into.
     Vector<GraphicsLayerPaintInfo> m_squashedLayers;
     LayoutPoint m_squashingLayerOffsetFromTransformedAncestor;
 
     LayoutRect m_compositedBounds;
 
     LayoutSize m_contentOffsetInCompositingLayer;
+
+    // We keep track of the scrolling contents offset, so that when it changes we can notify the ScrollingCoordinator, which
+    // passes on main-thread scrolling updates to the compositor.
+    DoubleSize m_scrollingContentsOffset;
+
     unsigned m_contentOffsetInCompositingLayerDirty : 1;
 
     unsigned m_pendingUpdateScope : 2;
     unsigned m_isMainFrameLayoutViewLayer : 1;
 
     unsigned m_backgroundLayerPaintsFixedRootBackground : 1;
     unsigned m_scrollingContentsAreEmpty : 1;
 
     friend class CompositedLayerMappingTest;
 };
 
 } // namespace blink
 
 #endif // CompositedLayerMapping_h