[New Multicolumn] Correct paint rectangle calculation for compositing.

Source/core/rendering/compositing/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 738 matching lines @@
 void RenderLayerCompositor::setOverlayLayer(GraphicsLayer* layer)
 {
     ASSERT(rootGraphicsLayer());
 
     if (layer->parent() != m_overflowControlsHostLayer.get())
         m_overflowControlsHostLayer->addChild(layer);
 }
 
 bool RenderLayerCompositor::canBeComposited(const RenderLayer* layer) const
 {
-    // FIXME: We disable accelerated compositing for elements in a RenderFlowThread as it doesn't work properly.
-    // See http://webkit.org/b/84900 to re-enable it.
-    return m_hasAcceleratedCompositing && layer->isSelfPaintingLayer() && !layer->subtreeIsInvisible() && layer->renderer()->flowThreadState() == RenderObject::NotInsideFlowThread;
+    return m_hasAcceleratedCompositing && layer->isSelfPaintingLayer() && !layer->subtreeIsInvisible();
 }
 
 // Return true if the given layer is a stacking context and has compositing child
 // layers that it needs to clip. In this case we insert a clipping GraphicsLayer
 // into the hierarchy between this layer and its children in the z-order hierarchy.
 bool RenderLayerCompositor::clipsCompositingDescendants(const RenderLayer* layer) const
 {
     return layer->hasCompositingDescendant() && layer->renderer()->hasClipOrOverflowClip();
 }
 
@@ skipping 418 matching lines @@
     } else if (graphicsLayer == m_scrollLayer.get()) {
         name = "LocalFrame Scrolling Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink