Rebuild GraphicsLayer tree when a LayoutPart's CDPLM configuration changes

Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 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 518 matching lines @@
         }
     } else if (layoutObject->isVideo()) {
         HTMLMediaElement* mediaElement = toHTMLMediaElement(layoutObject->node());
         m_graphicsLayer->setContentsToPlatformLayer(mediaElement->platformLayer());
     } else if (isAcceleratedCanvas(layoutObject)) {
         HTMLCanvasElement* canvas = toHTMLCanvasElement(layoutObject->node());
         if (CanvasRenderingContext* context = canvas->renderingContext())
             m_graphicsLayer->setContentsToPlatformLayer(context->platformLayer());
         layerConfigChanged = true;
     }
-    if (layoutObject->isLayoutPart())
-        layerConfigChanged = DeprecatedPaintLayerCompositor::parentFrameContentLayers(toLayoutPart(layoutObject));
+    if (layoutObject->isLayoutPart()) {
+        if (DeprecatedPaintLayerCompositor::parentFrameContentLayers(toLayoutPart(layoutObject)))
+            layerConfigChanged = true;
+    }
 
     // Changes to either the internal hierarchy or the mask layer have an impact
     // on painting phases, so we need to update when either are updated.
     if (layerConfigChanged || maskLayerChanged)
         updatePaintingPhases();
 
     return layerConfigChanged;
 }
 
 static IntRect clipBox(LayoutBox* layoutObject)
@@ skipping 1791 matching lines @@
     } else if (graphicsLayer == m_scrollingBlockSelectionLayer.get()) {
         name = "Scrolling Block Selection Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace blink