Move renderFallbackContent() into FrameOwner interface.

Source/web/RemoteBridgeFrameOwner.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be found
 // in the LICENSE file.
 
 #ifndef RemoteBridgeFrameOwner_h
 #define RemoteBridgeFrameOwner_h
 
 #include "core/frame/FrameOwner.h"
 #include "web/WebLocalFrameImpl.h"
 
 namespace blink {
 
 // Helper class to bridge communication for a frame with a remote parent.
 // Currently, it serves two purposes:
 // 1. Allows the local frame's loader to retrieve sandbox flags associated with
 //    its owner element in another process.
 // 2. Trigger a load event on its owner element once it finishes a load.
-class RemoteBridgeFrameOwner : public NoBaseWillBeGarbageCollectedFinalized<RemoteBridgeFrameOwner>, public FrameOwner {
+class RemoteBridgeFrameOwner final : public NoBaseWillBeGarbageCollectedFinalized<RemoteBridgeFrameOwner>, public FrameOwner {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(RemoteBridgeFrameOwner);
 public:
     static PassOwnPtrWillBeRawPtr<RemoteBridgeFrameOwner> create(PassRefPtrWillBeRawPtr<WebLocalFrameImpl> frame, SandboxFlags flags)
     {
         return adoptPtrWillBeNoop(new RemoteBridgeFrameOwner(frame, flags));
     }
 
-    virtual bool isLocal() const override
+    bool isLocal() const override
     {
         return false;
     }
 
-    virtual SandboxFlags sandboxFlags() const override
+    SandboxFlags sandboxFlags() const override
     {
         return m_sandboxFlags;
     }
 
     void setSandboxFlags(SandboxFlags flags)
     {
         m_sandboxFlags = flags;
     }
 
     void setContentFrame(PassRefPtrWillBeRawPtr<WebLocalFrameImpl> frame)
     {
         m_frame = frame;
     }
 
-    virtual void dispatchLoad() override;
+    void dispatchLoad() override;
+
+    void renderFallbackContent() override
+    {
+        // TODO(dcheng): Implement.
+    }
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     RemoteBridgeFrameOwner(PassRefPtrWillBeRawPtr<WebLocalFrameImpl>, SandboxFlags);
 
     RefPtrWillBeMember<WebLocalFrameImpl> m_frame;
     SandboxFlags m_sandboxFlags;
 };
 
 DEFINE_TYPE_CASTS(RemoteBridgeFrameOwner, FrameOwner, owner, !owner->isLocal(), !owner.isLocal());
 
 } // namespace blink
 
 #endif // RemoteBridgeFrameOwner_h