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

Source/core/rendering/RenderBox.cpp

Index: Source/core/rendering/RenderBox.cpp
diff --git a/Source/core/rendering/RenderBox.cpp b/Source/core/rendering/RenderBox.cpp
index 66f69da739efb2b2e5f3a5767ab01d4d59e8b263..12957a2d1e4a5127a732791ba5e607507337dd83 100644
--- a/Source/core/rendering/RenderBox.cpp
+++ b/Source/core/rendering/RenderBox.cpp
@@ -778,11 +778,10 @@ IntSize RenderBox::calculateAutoscrollDirection(const IntPoint& windowPoint) con
     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);
@@ -793,7 +792,8 @@ IntSize RenderBox::calculateAutoscrollDirection(const IntPoint& windowPoint) con
         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)