Add loadedNonEmptyDocument flag in iframe for Resource Timing

Source/core/html/HTMLFrameOwnerElement.h

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 42 matching lines @@
     RenderPart* renderPart() const;
 
 #if ENABLE(SVG)
     SVGDocument* getSVGDocument(ExceptionCode&) const;
 #endif
 
     virtual ScrollbarMode scrollingMode() const { return ScrollbarAuto; }
 
     SandboxFlags sandboxFlags() const { return m_sandboxFlags; }
 
+    virtual bool loadedNonEmptyDocument() const { return false; }
+    virtual void didLoadNonEmptyDocument() { }
+
 protected:
     HTMLFrameOwnerElement(const QualifiedName& tagName, Document*);
     void setSandboxFlags(SandboxFlags);
 
 private:
     virtual bool isKeyboardFocusable(KeyboardEvent*) const;
     virtual bool isFrameOwnerElement() const OVERRIDE { return true; }
 
     Frame* m_contentFrame;
     SandboxFlags m_sandboxFlags;
@@ skipping 33 matching lines @@
         DEFINE_STATIC_LOCAL(HashSet<Node*>, nodes, ());
         return nodes;
     }
 
     Node* m_root;
 };
 
 } // namespace WebCore
 
 #endif // HTMLFrameOwnerElement_h