Avoid mutating frame owner when detaching a provisional frame.

third_party/WebKit/Source/web/tests/FrameTestHelpers.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 219 matching lines @@
   TestWebViewClient* m_testWebViewClient;
 };
 
 // Minimal implementation of WebFrameClient needed for unit tests that load
 // frames. Tests that load frames and need further specialization of
 // WebFrameClient behavior should subclass this.
 class TestWebFrameClient : public WebFrameClient {
  public:
   TestWebFrameClient();
 
+  void frameDetached(WebLocalFrame*, DetachType) override;
   WebLocalFrame* createChildFrame(WebLocalFrame* parent,
                                   WebTreeScopeType,
                                   const WebString& name,
                                   const WebString& uniqueName,
                                   WebSandboxFlags,
                                   const WebFrameOwnerProperties&) override;
   void didStartLoading(bool) override;
   void didStopLoading() override;
 
   bool isLoading() { return m_loadsInProgress > 0; }
@@ skipping 19 matching lines @@
                           WebDOMMessageEvent) override {}
 
  private:
   Persistent<WebRemoteFrameImpl> const m_frame;
 };
 
 }  // namespace FrameTestHelpers
 }  // namespace blink
 
 #endif  // FrameTestHelpers_h