Fix drag-and-drop autoscrolling with --enable-pinch-virtual-viewport

Source/core/frame/PinchViewport.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 131 matching lines @@
     return rectInViewport;
 }
 
 void PinchViewport::scrollIntoView(const LayoutRect& rect)
 {
     if (!mainFrame() || !mainFrame()->view())
         return;
 
     FrameView* view = mainFrame()->view();
 
-    // Snap the visible rect to layout units to match the input rect.
-    FloatRect visible = LayoutRect(visibleRect());
+    // Snap the visible rect to layout units to match the input rect. Intersect
+    // with the FrameView so that we exclude scrollbars from the visible area.
+    FloatRect visible = intersection(
+        LayoutRect(visibleRectInDocument()),
+        LayoutRect(view->visibleContentRect()));
 
     float centeringOffsetX = (visible.width() - rect.width()) / 2;
     float centeringOffsetY = (visible.height() - rect.height()) / 2;
 
     DoublePoint targetOffset(
-        rect.x() - centeringOffsetX - visible.x(),
-        rect.y() - centeringOffsetY - visible.y());

[bokan, 2015/01/15 23:53:01]

visibleRect() is relative to the FrameView, since we now use
visibleRectInDocument, the adjustment here is no longer necessary.

+        rect.x() - centeringOffsetX,
+        rect.y() - centeringOffsetY);
 
     view->setScrollPosition(targetOffset);
 
     DoublePoint remainder = DoublePoint(targetOffset - view->scrollPositionDouble());
     move(toFloatPoint(remainder));
 }
 
 void PinchViewport::setLocation(const FloatPoint& newLocation)
 {
     setScaleAndLocation(m_scale, newLocation);
@@ skipping 375 matching lines @@
     } else if (graphicsLayer == m_rootTransformLayer) {
         name =  "Root Transform Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink