Fix position:sticky location bug when scroller is not a stacking context

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.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 301 matching lines @@
         ancestorOverflowLayer->getScrollableArea()->stickyConstraintsMap().at(
             &m_owningLayer);
 
     // Find the layout offset of the unshifted sticky box within its
     // compositingContainer. If the enclosing layer is not the scroller, then
     // the offset must be adjusted to include the scroll offset to keep it
     // relative to compositingContainer.
     LayoutPoint enclosingLayerOffset;
     compositingContainer->convertToLayerCoords(ancestorOverflowLayer,
                                                enclosingLayerOffset);
-    if (compositingContainer != ancestorOverflowLayer) {
+    DCHECK(!scrollParent() || scrollParent() == ancestorOverflowLayer);
+    if (!scrollParent() && compositingContainer != ancestorOverflowLayer) {
       enclosingLayerOffset += LayoutSize(
           ancestorOverflowLayer->getScrollableArea()->getScrollOffset());
     }
 
     FloatPoint stickyBoxOffset =
         constraints.scrollContainerRelativeStickyBoxRect().location();
     DCHECK(!m_contentOffsetInCompositingLayerDirty);
     stickyBoxOffset.moveBy(FloatPoint(-enclosingLayerOffset) -
                            FloatSize(contentOffsetInCompositingLayer()));
 
@@ skipping 3165 matching lines @@
   } else if (graphicsLayer == m_decorationOutlineLayer.get()) {
     name = "Decoration Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink