Avoid mutating frame owner when detaching a provisional frame.

third_party/WebKit/Source/web/RemoteFrameOwner.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 RemoteFrameOwner_h
 #define RemoteFrameOwner_h
 
 #include "core/frame/FrameOwner.h"
 #include "platform/scroll/ScrollTypes.h"
 #include "public/web/WebFrameOwnerProperties.h"
@@ skipping 11 matching lines @@
   USING_GARBAGE_COLLECTED_MIXIN(RemoteFrameOwner);
 
  public:
   static RemoteFrameOwner* create(
       SandboxFlags flags,
       const WebFrameOwnerProperties& frameOwnerProperties) {
     return new RemoteFrameOwner(flags, frameOwnerProperties);
   }
 
   // FrameOwner overrides:
+  Frame* contentFrame() const override { return m_frame.get(); }
   void setContentFrame(Frame&) override;
   void clearContentFrame() override;
   SandboxFlags getSandboxFlags() const override { return m_sandboxFlags; }
   void setSandboxFlags(SandboxFlags flags) { m_sandboxFlags = flags; }
   void dispatchLoad() override;
   // TODO(dcheng): Implement.
   bool canRenderFallbackContent() const override { return false; }
   void renderFallbackContent() override {}
   ScrollbarMode scrollingMode() const override { return m_scrolling; }
   int marginWidth() const override { return m_marginWidth; }
@@ skipping 43 matching lines @@
 
 DEFINE_TYPE_CASTS(RemoteFrameOwner,
                   FrameOwner,
                   owner,
                   owner->isRemote(),
                   owner.isRemote());
 
 }  // namespace blink
 
 #endif  // RemoteFrameOwner_h