Viewport apply scroll should be on the document element not scrollingElement.

third_party/WebKit/Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 1253 matching lines @@
     String m_rawTitle;
     Member<Element> m_titleElement;
 
     Member<AXObjectCache> m_axObjectCache;
     Member<DocumentMarkerController> m_markers;
 
     Timer<Document> m_updateFocusAppearanceTimer;
 
     Member<Element> m_cssTarget;
 
-    // Not a WeakMember since we want to keep the scrollingElement around until
-    // we move its ApplyScroll onto the new scrollingElement.
-    Member<Element> m_oldScrollingElement;
-
     LoadEventProgress m_loadEventProgress;
 
     double m_startTime;
 
     Member<ScriptRunner> m_scriptRunner;
 
     HeapVector<Member<HTMLScriptElement>> m_currentScriptStack;
 
     OwnPtr<TransformSource> m_transformSource;
 
@@ skipping 154 matching lines @@
 DEFINE_TYPE_CASTS(TreeScope, Document, document, true, true);
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLiveDocumentInstances();
 #endif
 
 #endif // Document_h