Don't set scroll client for main frame

Source/core/platform/graphics/GraphicsLayer.h

 /*
  * Copyright (C) 2009 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 407 matching lines @@
 
     static bool supportsBackgroundColorContent()
     {
         return false;
     }
 
     void setLinkHighlight(LinkHighlightClient*);
     // Exposed for tests
     LinkHighlightClient* linkHighlight() { return m_linkHighlight; }
 
-    void setScrollableArea(ScrollableArea* scrollableArea) { m_scrollableArea = scrollableArea; }
+    void setScrollableArea(ScrollableArea*, bool isMainFrame);
     ScrollableArea* scrollableArea() const { return m_scrollableArea; }
 
     WebKit::WebContentLayer* contentLayer() const { return m_layer.get(); }
 
     // Exposed for tests. FIXME - name is too similar to contentLayer(), very error prone.
     WebKit::WebLayer* contentsLayer() const { return m_contentsLayer; }
 
     void updateDebugIndicators();
 
     void reportMemoryUsage(MemoryObjectInfo*) const;
@@ skipping 133 matching lines @@
 
 
 } // namespace WebCore
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showGraphicsLayerTree(const WebCore::GraphicsLayer* layer);
 #endif
 
 #endif // GraphicsLayer_h