Don't update graphics layer positions during coordinated scrolling

Source/core/page/scrolling/ScrollingCoordinator.h

Index: Source/core/page/scrolling/ScrollingCoordinator.h
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.h b/Source/core/page/scrolling/ScrollingCoordinator.h
index 925583bf4ee1157d9bd1b9828cda54672eb71a64..4de491338aa88d62d7296747c257c2167be2413b 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.h
+++ b/Source/core/page/scrolling/ScrollingCoordinator.h
@@ -90,7 +90,8 @@ public:
     bool shouldUpdateScrollLayerPositionOnMainThread() const { return mainThreadScrollingReasons() != 0; }
 
     void willDestroyScrollableArea(ScrollableArea*);
-    void scrollableAreaScrollLayerDidChange(ScrollableArea*);
+    // Returns true iff the coordinator handled this change.

[jamesr, 2013/07/09 23:39:38]

while iff is more precise than if, i don't think it's used very widely in blink
compared to 'if' so we should probably just use that. just don't tell my
geometry teacher!

[enne (OOO), 2013/07/09 23:43:47]

Iff you say so.  Done.

+    bool scrollableAreaScrollLayerDidChange(ScrollableArea*);
     void scrollableAreaScrollbarLayerDidChange(ScrollableArea*, ScrollbarOrientation);
     void setLayerIsContainerForFixedPositionLayers(GraphicsLayer*, bool);
     void updateLayerPositionConstraint(RenderLayer*);