Drag'n drop Autoscroll does not work properly on inner frames

Source/core/rendering/RenderBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 760 matching lines @@
 // scrolling.
 IntSize RenderBox::calculateAutoscrollDirection(const IntPoint& windowPoint) const
 {
     if (!frame())
         return IntSize();
 
     FrameView* frameView = frame()->view();
     if (!frameView)
         return IntSize();
 
-    IntSize offset;
-    IntPoint point = frameView->windowToContents(windowPoint);
-    IntRect box(absoluteBoundingBoxRect());
-    if (isRenderView())
-        box.moveBy(frameView->windowToContents(IntPoint()));
+    IntPoint point = windowPoint;

[yosin_UTC9, 2013/09/10 02:09:38]

nit: can we introduce new variable windowAutoscrollPoint, or another to denote
we are on window coordinate?

+    IntRect box((absoluteBoundingBoxRect()));
+    box.move(view()->frameView()->scrollOffset());
+    box = view()->frameView()->contentsToWindow(box);

[yosin_UTC9, 2013/09/10 02:09:38]

nit: can we introduce new variable windowBox to denote we are on window
coordinate?

 
     if (point.x() < box.x() + autoscrollBeltSize)
         point.move(-autoscrollBeltSize, 0);
     else if (point.x() > box.maxX() - autoscrollBeltSize)
         point.move(autoscrollBeltSize, 0);
 
     if (point.y() < box.y() + autoscrollBeltSize)
         point.move(0, -autoscrollBeltSize);
     else if (point.y() > box.maxY() - autoscrollBeltSize)
         point.move(0, autoscrollBeltSize);
-    return frameView->contentsToWindow(point) - windowPoint;
+
+    return point - windowPoint;
 }
 
 RenderBox* RenderBox::findAutoscrollable(RenderObject* renderer)
 {
     while (renderer && !(renderer->isBox() && toRenderBox(renderer)->canAutoscroll())) {
         if (!renderer->parent() && renderer->node() == &renderer->document() && renderer->document().ownerElement())
             renderer = renderer->document().ownerElement()->renderer();
         else
             renderer = renderer->parent();
     }
@@ skipping 3903 matching lines @@
     }
 
     if (didSplitParentAnonymousBoxes)
         markBoxForRelayoutAfterSplit(this);
 
     ASSERT(beforeChild->parent() == this);
     return beforeChild;
 }
 
 } // namespace WebCore