Add a setting to do frame scrolls through the root layer.

Source/core/rendering/RenderLayerScrollableArea.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 181 matching lines @@
         }
     } else {
         if (GraphicsLayer* layer = layerForHorizontalScrollbar()) {
             layer->setNeedsDisplayInRect(rect, PaintInvalidationScroll);
             return;
         }
     }
 
     IntRect scrollRect = rect;
     // If we are not yet inserted into the tree, there is no need to issue paint invaldiations.
-    if (!box().parent())
+    if (!box().isRenderView() && !box().parent())
         return;
 
     if (scrollbar == m_vBar.get())
         scrollRect.move(verticalScrollbarStart(0, box().width()), box().borderTop());
     else
         scrollRect.move(horizontalScrollbarStart(0), box().height() - box().borderBottom() - scrollbar->height());
 
     if (scrollRect.isEmpty())
         return;
 
@@ skipping 1275 matching lines @@
 void RenderLayerScrollableArea::setTopmostScrollChild(RenderLayer* scrollChild)
 {
     // We only want to track the topmost scroll child for scrollable areas with
     // overlay scrollbars.
     if (!hasOverlayScrollbars())
         return;
     m_nextTopmostScrollChild = scrollChild;
 }
 
 } // namespace blink