We have a problem in the process on destroying WebContentsImpl because

content/shell/browser/shell.cc

 // Copyright 2013 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.
 
 #include "content/shell/browser/shell.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/message_loop/message_loop.h"
 #include "base/path_service.h"
@@ skipping 29 matching lines @@
 bool Shell::quit_message_loop_ = true;
 
 class Shell::DevToolsWebContentsObserver : public WebContentsObserver {
  public:
   DevToolsWebContentsObserver(Shell* shell, WebContents* web_contents)
       : WebContentsObserver(web_contents),
         shell_(shell) {
   }
 
   // WebContentsObserver
-  virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE {
+  virtual void WebContentsDestroyed() OVERRIDE {
     shell_->OnDevToolsWebContentsDestroyed();
   }
 
  private:
   Shell* shell_;
 
   DISALLOW_COPY_AND_ASSIGN(DevToolsWebContentsObserver);
 };
 
 Shell::Shell(WebContents* web_contents)
@@ skipping 329 matching lines @@
   devtools_frontend_->Activate();
   devtools_frontend_->Focus();
 }
 
 void Shell::OnDevToolsWebContentsDestroyed() {
   devtools_observer_.reset();
   devtools_frontend_ = NULL;
 }
 
 }  // namespace content