Fix paint invalidation for composited vertical-rl having overflow

third_party/WebKit/Source/core/layout/LayoutView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 276 matching lines @@
     if (RuntimeEnabledFeatures::rootLayerScrollingEnabled())
         return LayoutBlockFlow::visualOverflowRect();
 
     // Ditto when not in compositing mode.
     if (!usesCompositing())
         return LayoutBlockFlow::visualOverflowRect();
 
     // In normal compositing mode, LayoutView doesn't actually apply clipping
     // on its descendants. Instead their visual overflow is propagated to
     // compositor()->m_rootContentLayer for accelerated scrolling.
-    return LayoutRect(documentRect());
+    return layoutOverflowRect();
 }
 
 LayoutRect LayoutView::localOverflowRectForPaintInvalidation() const
 {
     // TODO(wangxianzhu): This is only required without rootLayerScrolls (though it is also correct
     // but unnecessary with rootLayerScrolls) because of the special LayoutView overflow model.
     return visualOverflowRect();
 }
 
 void LayoutView::mapLocalToAncestor(const LayoutBoxModelObject* ancestor, TransformState& transformState, MapCoordinatesFlags mode) const
@@ skipping 507 matching lines @@
     if (hasOverflowClip())
         excludeScrollbars(rect, overlayScrollbarClipBehavior);
 
     return rect;
 }
 
 IntRect LayoutView::documentRect() const
 {
     LayoutRect overflowRect(layoutOverflowRect());
     flipForWritingMode(overflowRect);
+    // TODO(crbug.com/650768): The pixel snapping looks incorect.

[chrishtr, 2016/09/27 18:55:20]

nit: "incorrect"

[Xianzhu, 2016/09/27 20:48:38]

Done.

     return pixelSnappedIntRect(overflowRect);
 }
 
 bool LayoutView::rootBackgroundIsEntirelyFixed() const
 {
     return style()->hasEntirelyFixedBackground();
 }
 
 LayoutRect LayoutView::backgroundRect(LayoutBox* backgroundLayoutObject) const
 {
@@ skipping 170 matching lines @@
     if (block)
         block->adjustChildDebugRect(rect);
 
     rect.setWidth(LayoutUnit(viewWidth(IncludeScrollbars)));
     rect.setHeight(LayoutUnit(viewHeight(IncludeScrollbars)));
 
     return rect;
 }
 
 } // namespace blink