Move renderFallbackContent() into FrameOwner interface.

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 45 matching lines @@
     // LayoutObject when using fallback content.
     LayoutPart* layoutPart() const;
 
     Document* getSVGDocument(ExceptionState&) const;
 
     virtual ScrollbarMode scrollingMode() const { return ScrollbarAuto; }
 
     virtual bool loadedNonEmptyDocument() const { return false; }
     virtual void didLoadNonEmptyDocument() { }
 
-    virtual void renderFallbackContent() { }
-
-    virtual bool isObjectElement() const { return false; }
     void setWidget(PassRefPtrWillBeRawPtr<Widget>);
     Widget* ownedWidget() const;
 
     class UpdateSuspendScope {
     public:
         UpdateSuspendScope();
         ~UpdateSuspendScope();
 
     private:
         void performDeferredWidgetTreeOperations();
     };
 
     // FrameOwner overrides:
-    virtual bool isLocal() const { return true; }
-    virtual void dispatchLoad() override;
-    virtual SandboxFlags sandboxFlags() const override { return m_sandboxFlags; }
+    bool isLocal() const override { return true; }
+    void dispatchLoad() override;
+    SandboxFlags sandboxFlags() const override { return m_sandboxFlags; }
+    void renderFallbackContent() override { }
 
     DECLARE_VIRTUAL_TRACE();
 
 protected:
     HTMLFrameOwnerElement(const QualifiedName& tagName, Document&);
     void setSandboxFlags(SandboxFlags);
 
     bool loadOrRedirectSubframe(const KURL&, const AtomicString& frameName, bool lockBackForwardList);
 
 private:
@@ skipping 36 matching lines @@
     static WillBeHeapHashCountedSet<RawPtrWillBeMember<Node>>& disabledSubtreeRoots();
 
     RawPtrWillBeMember<Node> m_root;
 };
 
 DEFINE_TYPE_CASTS(HTMLFrameOwnerElement, FrameOwner, owner, owner->isLocal(), owner.isLocal());
 
 } // namespace blink
 
 #endif // HTMLFrameOwnerElement_h