Fix PaintLayer::compositingContainer for self-painting non-stacked layers

third_party/WebKit/Source/core/paint/PaintLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 904 matching lines @@
                                 FloatPoint());
   layoutObject()->mapLocalToAncestor(
       transformAncestor() ? transformAncestor()->layoutObject() : nullptr,
       transformState, 0);
   transformState.flatten();
   return LayoutPoint(transformState.lastPlanarPoint());
 }
 
 PaintLayer* PaintLayer::compositingContainer() const {
   if (!stackingNode()->isStacked())
-    return containingLayer();
+    return isSelfPaintingLayer() ? parent() : containingLayer();
   if (PaintLayerStackingNode* ancestorStackingNode =
           stackingNode()->ancestorStackingContextNode())
     return ancestorStackingNode->layer();
   return nullptr;
 }
 
 bool PaintLayer::isPaintInvalidationContainer() const {
   return compositingState() == PaintsIntoOwnBacking ||
          compositingState() == PaintsIntoGroupedBacking;
 }
@@ skipping 2255 matching lines @@
 }
 
 void showLayerTree(const blink::LayoutObject* layoutObject) {
   if (!layoutObject) {
     LOG(INFO) << "Cannot showLayerTree. Root is (nil)";
     return;
   }
   showLayerTree(layoutObject->enclosingLayer());
 }
 #endif