Don't force-update style and layout in Document::scrollingElement

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 2064 matching lines @@
 void CompositedLayerMapping::updateElementIdAndCompositorMutableProperties() {
   int elementId = 0;
   uint32_t primaryMutableProperties = CompositorMutableProperty::kNone;
   uint32_t scrollMutableProperties = CompositorMutableProperty::kNone;
 
   Node* owningNode = m_owningLayer.layoutObject()->node();
   Element* animatingElement = nullptr;
   const ComputedStyle* animatingStyle = nullptr;
   if (owningNode) {
     Document& document = owningNode->document();
-    Element* scrollingElement = document.scrollingElement();
+    Element* scrollingElement = document.scrollingElementNoLayout();
     if (owningNode->isElementNode() &&
         (!RuntimeEnabledFeatures::rootLayerScrollingEnabled() ||
          owningNode != scrollingElement)) {
       animatingElement = toElement(owningNode);
       animatingStyle = m_owningLayer.layoutObject()->style();
     } else if (owningNode->isDocumentNode() &&
                RuntimeEnabledFeatures::rootLayerScrollingEnabled()) {
       owningNode = animatingElement = scrollingElement;
       if (scrollingElement && scrollingElement->layoutObject())
         animatingStyle = scrollingElement->layoutObject()->style();
@@ skipping 1348 matching lines @@
   } else if (graphicsLayer == m_decorationOutlineLayer.get()) {
     name = "Decoration Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink