Fix const correctness of containerForRepaint

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 1545 matching lines @@
     // FIXME: SVG should probably also go through this unified repaint system.
 
     ASSERT(RuntimeEnabledFeatures::repaintAfterLayoutEnabled());
     ASSERT(!needsLayout());
 
     if (!shouldCheckForInvalidationAfterLayout())
         return;
 
     const LayoutRect oldRepaintRect = previousRepaintRect();
     const LayoutPoint oldPositionFromRepaintContainer = previousPositionFromRepaintContainer();
-    RenderLayerModelObject* repaintContainer = containerForRepaint();
+    const RenderLayerModelObject* repaintContainer = containerForRepaint();
     setPreviousRepaintRect(clippedOverflowRectForRepaint(repaintContainer));
     setPreviousPositionFromRepaintContainer(positionFromRepaintContainer(repaintContainer));
 
     // If we are set to do a full repaint that means the RenderView will be
     // invalidated. We can then skip issuing of invalidations for the child
     // renderers as they'll be covered by the RenderView.
     if (view()->doingFullRepaint() && this != view()) {
         LayoutStateMaintainer statePusher(*this, isTableRow() ? LayoutSize() : locationOffset());
         RenderObject::repaintTreeAfterLayout();
         return;
@@ skipping 3092 matching lines @@
         return 0;
 
     if (!layoutState && !flowThreadContainingBlock())
         return 0;
 
     RenderBlock* containerBlock = containingBlock();
     return containerBlock->offsetFromLogicalTopOfFirstPage() + logicalTop();
 }
 
 } // namespace WebCore