Use full mapLocalToAncestor machinery in ScrollingCoordinator.

third_party/WebKit/Source/core/frame/VisualViewport.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 575 matching lines @@
 
 void VisualViewport::setBrowserControlsAdjustment(float adjustment) {
   m_browserControlsAdjustment = adjustment;
 }
 
 float VisualViewport::browserControlsAdjustment() const {
   return m_browserControlsAdjustment;
 }
 
 IntRect VisualViewport::scrollableAreaBoundingBox() const {
-  // This method should return the bounding box in the parent view's coordinate
-  // space; however, VisualViewport technically isn't a child of any Frames.
-  // Nonetheless, the VisualViewport always occupies the entire main frame so
-  // just return that.
+  // This method should return the bounding box in the top-level FrameView's
+  // coordinate space; however, VisualViewport technically isn't a child of any
+  // Frames.  Nonetheless, the VisualViewport always occupies the entire main
+  // frame so just return that.
   LocalFrame* frame = mainFrame();
 
   if (!frame || !frame->view())
     return IntRect();
 
   return frame->view()->frameRect();
 }
 
 IntSize VisualViewport::contentsSize() const {
   LocalFrame* frame = mainFrame();
@@ skipping 238 matching lines @@
   } else if (graphicsLayer == m_rootTransformLayer.get()) {
     name = "Root Transform Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink