Reland "Implement FullScreen using top layer."

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 1331 matching lines @@
     bool m_sawElementsInKnownNamespaces;
     bool m_isSrcdocDocument;
     bool m_isMobileDocument;
 
     LayoutView* m_layoutView;
 
     WeakMember<Document> m_contextDocument;
 
     bool m_hasFullscreenSupplement; // For early return in Fullscreen::fromIfExists()
 
+    // The last element in |m_topLayerElements| is topmost in the top layer
+    // stack and is thus the one that will be visually on top.
     HeapVector<Member<Element>> m_topLayerElements;
 
     int m_loadEventDelayCount;
     Timer<Document> m_loadEventDelayTimer;
     Timer<Document> m_pluginLoadingTimer;
 
     ViewportDescription m_viewportDescription;
     ViewportDescription m_legacyViewportDescription;
     Length m_viewportDefaultMinWidth;
 
@@ skipping 94 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