Don't paint self-painting frameset frames in the layout tree paint recursion.

Source/core/paint/FrameSetPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/FrameSetPainter.h"
 
 #include "core/html/HTMLFrameSetElement.h"
 #include "core/layout/LayoutFrameSet.h"
 #include "core/paint/LayoutObjectDrawingRecorder.h"
@@ skipping 92 matching lines @@
             yPos += borderThickness;
         }
     }
 }
 
 void FrameSetPainter::paintChildren(const PaintInfo& paintInfo, const LayoutPoint& adjustedPaintOffset)
 {
     // Paint only those children that fit in the grid.
     // Remaining frames are "hidden".
     // See also LayoutFrameSet::positionFrames.
     LayoutObject* child = m_layoutFrameSet.firstChild();

[wkorman, 2015/06/12 19:14:48]

It looks like this could be null, at least theoretically, per:

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

If so, add null check?

     size_t rows = m_layoutFrameSet.rows().m_sizes.size();
     size_t cols = m_layoutFrameSet.columns().m_sizes.size();
     for (size_t r = 0; r < rows; r++) {
         for (size_t c = 0; c < cols; c++) {
+            if (child->isLayoutBoxModelObject() && toLayoutBoxModelObject(child)->hasSelfPaintingLayer())

[wkorman, 2015/06/12 19:14:48]

Worth adding a comment on why we do this?

[chrishtr, 2015/06/12 19:57:28]

Done.

+                continue;
             child->paint(paintInfo, adjustedPaintOffset);
             child = child->nextSibling();
             if (!child)
                 return;
         }
     }
 }
 
 void FrameSetPainter::paint(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     if (paintInfo.phase != PaintPhaseForeground)
         return;
 
     LayoutObject* child = m_layoutFrameSet.firstChild();
     if (!child)
         return;
 
     LayoutPoint adjustedPaintOffset = paintOffset + m_layoutFrameSet.location();
     paintChildren(paintInfo, adjustedPaintOffset);
     paintBorders(paintInfo, adjustedPaintOffset);
 }
 
 } // namespace blink