Fold ScrollingCoordinatorChromium into ScrollingCoordinator and devirtualize

Source/WebCore/page/FrameView.h

Index: Source/WebCore/page/FrameView.h
diff --git a/Source/WebCore/page/FrameView.h b/Source/WebCore/page/FrameView.h
index bba3bae4438bac73ec23a6ff956c7604101f90a4..07bbb828abc142c99aff204e17b91d4dca01235e 100644
--- a/Source/WebCore/page/FrameView.h
+++ b/Source/WebCore/page/FrameView.h
@@ -132,10 +132,6 @@ public:
     void setNeedsOneShotDrawingSynchronization();
 
     virtual TiledBacking* tiledBacking() OVERRIDE;
-
-    // In the future when any ScrollableArea can have a node in th ScrollingTree, this should
-    // become a virtual function on ScrollableArea.
-    uint64_t scrollLayerID() const;
 #endif
 
     bool hasCompositedContent() const;