Revert changes is the use of CompositingReasonOutOfFlowClipping

third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.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 261 matching lines @@
             }
             if (layer->scrollsWithRespectTo(unclippedDescendant))
                 reasonsToComposite |= CompositingReasonAssumedOverlap;
         }
 
         // Remove irrelevant unclipped descendants in reverse order so our stored
         // indices remain valid.
         for (size_t i = 0; i < unclippedDescendantsToRemove.size(); i++)
             unclippedDescendants.remove(unclippedDescendantsToRemove.at(unclippedDescendantsToRemove.size() - i - 1));
 
-        if (layer->clipParent()) {
+        if (reasonsToComposite & CompositingReasonOutOfFlowClipping) {
             // TODO(schenney): We only need to promote when the clipParent is not a descendant of the ancestor scroller,
             // which we do not check for here. Hence we might be promoting needlessly.
             unclippedDescendants.append(layer);
         }
     }
 
     const IntRect& absBounds = layer->clippedAbsoluteBoundingBox();
     absoluteDescendantBoundingBox = absBounds;
 
     if (currentRecursionData.m_testingOverlap && !requiresCompositingOrSquashing(directReasons))
@@ skipping 154 matching lines @@
             overlapMap.finishCurrentOverlapTestingContext();
 
         descendantHas3DTransform |= anyDescendantHas3DTransform || layer->has3DTransform();
     }
 
     // At this point we have finished collecting all reasons to composite this layer.
     layer->setCompositingReasons(reasonsToComposite);
 }
 
 } // namespace blink