Only report bounding box touch hit rect for non-composited scroll layers.

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 3867 matching lines @@
     }
 }
 
 void RenderLayer::addLayerHitTestRects(LayerHitTestRects& rects) const
 {
     if (!size().isEmpty()) {
         Vector<LayoutRect> rect;
 
         if (renderBox() && renderBox()->scrollsOverflow()) {
             // For scrolling layers, rects are taken to be in the space of the contents.
-            // We need to include both the entire contents, and also the bounding box
-            // of the layer in the space of it's parent (eg. for border / scroll bars).
-            rect.append(m_scrollableArea->overflowRect());
+            // We need to include the bounding box of the layer in the space of its parent
+            // (eg. for border / scroll bars) and if it's composited then the entire contents
+            // as well as they may be on another composited layer. Skip reporting contents
+            // for non-composited layers as they'll get projected to the same layer as the
+            // bounding box.
+            if (compositingState() != NotComposited)
+                rect.append(m_scrollableArea->overflowRect());
+
             rects.set(this, rect);
             if (const RenderLayer* parentLayer = parent()) {
                 LayerHitTestRects::iterator iter = rects.find(parentLayer);
                 if (iter == rects.end())
                     iter = rects.add(parentLayer, Vector<LayoutRect>()).iterator;
                 iter->value.append(boundingBox(parentLayer));
             }
         } else {
             rect.append(localBoundingBox());
             rects.set(this, rect);
@@ skipping 18 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif