Move renderFallbackContent() into FrameOwner interface.

Source/core/html/HTMLObjectElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2006, 2007, 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 37 matching lines @@
     virtual bool hasFallbackContent() const override;
     virtual bool useFallbackContent() const override;
     virtual void renderFallbackContent() override;
 
     virtual bool isFormControlElement() const override { return false; }
 
     virtual bool isEnumeratable() const override { return true; }
     virtual bool isInteractiveContent() const override;
     virtual bool appendFormData(FormDataList&, bool) override;
 
-    virtual bool isObjectElement() const override { return true; }
-
     // Implementations of constraint validation API.
     // Note that the object elements are always barred from constraint validation.
     virtual String validationMessage() const override { return String(); }
     bool checkValidity() { return true; }
     bool reportValidity() { return true; }
     virtual void setCustomValidity(const String&) override { }
 
 #if !ENABLE(OILPAN)
     using Node::ref;
     using Node::deref;
@@ skipping 73 matching lines @@
     const HTMLObjectElement& objectElement = static_cast<const HTMLObjectElement&>(element);
     // We need to assert after the cast because FormAssociatedElement doesn't
     // have hasTagName.
     ASSERT_WITH_SECURITY_IMPLICATION(objectElement.hasTagName(HTMLNames::objectTag));
     return objectElement;
 }
 
 } // namespace blink
 
 #endif // HTMLObjectElement_h