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 270 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 &&
@@ skipping 173 matching lines @@
 
     descendantHas3DTransform |=
         anyDescendantHas3DTransform || layer->has3DTransform();
   }
 
   // At this point we have finished collecting all reasons to composite this layer.
   layer->setCompositingReasons(reasonsToComposite);
 }
 
 }  // namespace blink