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

Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.cpp b/Source/core/page/scrolling/ScrollingCoordinator.cpp
index dd5459233f8db3b8a74d7e3dcdf3b9fa64af4f44..26291466a173e59bd53c3172d4fc6487e2d05445 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -159,8 +159,9 @@ void ScrollingCoordinator::updateAfterCompositingChange()
     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()));