Remove the HasOwnBackingButPaintsIntoAncestor compositing state.

Source/core/rendering/compositing/CompositingLayerAssigner.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Google 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
@@ skipping 257 matching lines @@
         }
     }
 
     if (layer->stackingNode()->isStackingContext()) {
         RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), NegativeZOrderChildren);
         while (RenderLayerStackingNode* curNode = iterator.next())
             assignLayersToBackingsInternal(curNode->layer(), squashingState, layersNeedingPaintInvalidation);
     }
 
     if (m_layerSquashingEnabled) {
-        // At this point, if the layer is to be "separately" composited, then its backing becomes the most recent in paint-order.
-        if (layer->compositingState() == PaintsIntoOwnBacking || layer->compositingState() == HasOwnBackingButPaintsIntoAncestor) {
+        // At this point, if the layer is to be separately composited, then its backing becomes the most recent in paint-order.
+        if (layer->compositingState() == PaintsIntoOwnBacking) {
             ASSERT(!requiresSquashing(layer->compositingReasons()));
             squashingState.updateSquashingStateForNewMapping(layer->compositedLayerMapping(), layer->hasCompositedLayerMapping());
         }
     }
 
     if (layer->scrollParent())
         layer->scrollParent()->scrollableArea()->setTopmostScrollChild(layer);
 
     if (layer->needsCompositedScrolling())
         layer->scrollableArea()->setTopmostScrollChild(0);
 
     RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), NormalFlowChildren | PositiveZOrderChildren);
     while (RenderLayerStackingNode* curNode = iterator.next())
         assignLayersToBackingsInternal(curNode->layer(), squashingState, layersNeedingPaintInvalidation);
 
     if (squashingState.hasMostRecentMapping && &squashingState.mostRecentMapping->owningLayer() == layer)
         squashingState.haveAssignedBackingsToEntireSquashingLayerSubtree = true;
 }
 
 }