Large canvas does not honor containing div's border radius

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 1299 matching lines @@
 
 void RenderBox::paintMask(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     if (!paintInfo.shouldPaintWithinRoot(this) || style()->visibility() != VISIBLE || paintInfo.phase != PaintPhaseMask || paintInfo.context->paintingDisabled())
         return;
 
     LayoutRect paintRect = LayoutRect(paintOffset, size());
     paintMaskImages(paintInfo, paintRect);
 }
 
+void RenderBox::paintClippingMask(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
+{
+    if (!paintInfo.shouldPaintWithinRoot(this) || style()->visibility() != VISIBLE || paintInfo.phase != PaintPhaseClippingMask || paintInfo.context->paintingDisabled())
+        return;
+
+    if (!layer() || !layer()->isComposited())
+        return;
+
+    LayoutRect paintRect = LayoutRect(paintOffset, size());
+    paintInfo.context->fillRect(pixelSnappedIntRect(paintRect), Color::black);
+}
+
 void RenderBox::paintMaskImages(const PaintInfo& paintInfo, const LayoutRect& paintRect)
 {
     // Figure out if we need to push a transparency layer to render our mask.
     bool pushTransparencyLayer = false;
     bool compositedMask = hasLayer() && layer()->hasCompositedMask();
     bool flattenCompositingLayers = view()->frameView() && view()->frameView()->paintBehavior() & PaintBehaviorFlattenCompositingLayers;
     CompositeOperator compositeOp = CompositeSourceOver;
 
     bool allMaskImagesLoaded = true;
 
@@ skipping 3392 matching lines @@
         return 0;
 
     if (!layoutState && !flowThreadContainingBlock())
         return 0;
 
     RenderBlock* containerBlock = containingBlock();
     return containerBlock->offsetFromLogicalTopOfFirstPage() + logicalTop();
 }
 
 } // namespace WebCore