OOPIF: Replicate allowFullscreen flag.

third_party/WebKit/Source/core/html/HTMLIFrameElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  * Copyright (C) 2004, 2006, 2008, 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.
@@ skipping 41 matching lines @@
     LayoutObject* createLayoutObject(const ComputedStyle&) override;
 
     bool loadedNonEmptyDocument() const override { return m_didLoadNonEmptyDocument; }
     void didLoadNonEmptyDocument() override { m_didLoadNonEmptyDocument = true; }
     bool isInteractiveContent() const override;
 
     void valueWasSet() override;
 
     ReferrerPolicy referrerPolicyAttribute() override;
 
+    bool allowFullscreen() const override { return m_allowFullscreen; }
+
     AtomicString m_name;
     bool m_didLoadNonEmptyDocument;
+    bool m_allowFullscreen;
     Member<HTMLIFrameElementSandbox> m_sandbox;
 
     ReferrerPolicy m_referrerPolicy;
 };
 
 } // namespace blink
 
 #endif // HTMLIFrameElement_h