Main frame should remain scrollable if the fullscreen element is the document

Source/core/page/scrolling/ScrollingCoordinator.cpp

 /*
  * Copyright (C) 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 141 matching lines @@
         setShouldUpdateScrollLayerPositionOnMainThread(mainThreadScrollingReasons());
         m_shouldScrollOnMainThreadDirty = false;
     }
     m_wasFrameScrollable = frameIsScrollable;
 
     // The mainFrame view doesn't get included in the FrameTree below, so we
     // update its size separately.
     if (WebLayer* scrollingWebLayer = frameView ? toWebLayer(frameView->layerForScrolling()) : 0) {
         scrollingWebLayer->setBounds(frameView->contentsSize());
         // If there is a fullscreen element, set the scroll clip layer to 0 so main frame won't scroll.
-        Element* fullscreenElement = FullscreenElementStack::fullscreenElementFrom(*(m_page->mainFrame()->document()));
-        if (fullscreenElement)
+        Document* mainFrameDocument = m_page->mainFrame()->document();
+        Element* fullscreenElement = FullscreenElementStack::fullscreenElementFrom(*mainFrameDocument);
+        if (fullscreenElement && fullscreenElement != mainFrameDocument->documentElement())
             scrollingWebLayer->setScrollClipLayer(0);
         else
             scrollingWebLayer->setScrollClipLayer(toWebLayer(frameView->layerForContainer()));
     }
 
     const FrameTree& tree = m_page->mainFrame()->tree();
     for (const LocalFrame* child = tree.firstChild(); child; child = child->tree().nextSibling()) {
         if (WebLayer* scrollLayer = toWebLayer(child->view()->layerForScrolling()))
             scrollLayer->setBounds(child->view()->contentsSize());
     }
@@ skipping 802 matching lines @@
     bool frameIsScrollable = frameView && frameView->isScrollable();
     if (frameIsScrollable != m_wasFrameScrollable)
         return true;
 
     if (WebLayer* scrollLayer = frameView ? toWebLayer(frameView->layerForScrolling()) : 0)
         return blink::WebSize(frameView->contentsSize()) != scrollLayer->bounds();
     return false;
 }
 
 } // namespace WebCore