We have a problem in the process on destroying WebContentsImpl because

content/browser/browser_plugin/browser_plugin_guest.cc

 // Copyright (c) 2012 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/browser/browser_plugin/browser_plugin_guest.h"
 
 #include <algorithm>
 
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_util.h"
@@ skipping 150 matching lines @@
  public:
   explicit EmbedderWebContentsObserver(BrowserPluginGuest* guest)
       : WebContentsObserver(guest->embedder_web_contents()),
         browser_plugin_guest_(guest) {
   }
 
   virtual ~EmbedderWebContentsObserver() {
   }
 
   // WebContentsObserver:
-  virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE {
+  virtual void WebContentsDestroyed() OVERRIDE {
     browser_plugin_guest_->EmbedderDestroyed();
   }
 
   virtual void WasShown() OVERRIDE {
     browser_plugin_guest_->EmbedderVisibilityChanged(true);
   }
 
   virtual void WasHidden() OVERRIDE {
     browser_plugin_guest_->EmbedderVisibilityChanged(false);
   }
@@ skipping 1343 matching lines @@
     const GURL& url) {
   if (!url.is_valid()) {
     callback.Run(false);
     return;
   }
 
   delegate_->CanDownload(request_method, url, callback);
 }
 
 }  // namespace content