We have a problem in the process on destroying WebContentsImpl because

chrome/browser/ui/tab_contents/core_tab_helper.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 "chrome/browser/ui/tab_contents/core_tab_helper.h"
 
 #include <string>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 132 matching lines @@
 
 void CoreTabHelper::DidStartLoading(content::RenderViewHost* render_view_host) {
   UpdateContentRestrictions(0);
 }
 
 void CoreTabHelper::WasShown() {
   WebCacheManager::GetInstance()->ObserveActivity(
       web_contents()->GetRenderProcessHost()->GetID());
 }
 
-void CoreTabHelper::WebContentsDestroyed(WebContents* web_contents) {
+void CoreTabHelper::WebContentsDestroyed() {
   // OnCloseStarted isn't called in unit tests.
   if (!close_start_time_.is_null()) {
     bool fast_tab_close_enabled = CommandLine::ForCurrentProcess()->HasSwitch(
         switches::kEnableFastUnload);
 
     if (fast_tab_close_enabled) {
       base::TimeTicks now = base::TimeTicks::Now();
       base::TimeDelta close_time = now - close_start_time_;
       UMA_HISTOGRAM_TIMES("Tab.Close", close_time);
 
@@ skipping 84 matching lines @@
     DCHECK(!content_type.empty());
     open_url_params.uses_post = true;
     open_url_params.browser_initiated_post_data =
         base::RefCountedString::TakeString(post_data);
     open_url_params.extra_headers += base::StringPrintf(
         "%s: %s\r\n", net::HttpRequestHeaders::kContentType,
         content_type.c_str());
   }
   web_contents()->OpenURL(open_url_params);
 }