We have a problem in the process on destroying WebContentsImpl because

chrome/browser/printing/background_printing_manager.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/printing/background_printing_manager.h"
 
 #include "base/stl_util.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/printing/print_job.h"
 #include "chrome/browser/printing/print_preview_dialog_controller.h"
@@ skipping 10 matching lines @@
 
 namespace printing {
 
 class BackgroundPrintingManager::Observer
     : public content::WebContentsObserver {
  public:
   Observer(BackgroundPrintingManager* manager, WebContents* web_contents);
 
  private:
   virtual void RenderProcessGone(base::TerminationStatus status) OVERRIDE;
-  virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE;
+  virtual void WebContentsDestroyed() OVERRIDE;
 
   BackgroundPrintingManager* manager_;
 };
 
 BackgroundPrintingManager::Observer::Observer(
     BackgroundPrintingManager* manager, WebContents* web_contents)
     : content::WebContentsObserver(web_contents),
       manager_(manager) {
 }
 
 void BackgroundPrintingManager::Observer::RenderProcessGone(
     base::TerminationStatus status) {
   manager_->DeletePreviewContents(web_contents());
 }
-void BackgroundPrintingManager::Observer::WebContentsDestroyed(
-    WebContents* web_contents) {
-  manager_->DeletePreviewContents(web_contents);
+void BackgroundPrintingManager::Observer::WebContentsDestroyed() {
+  manager_->DeletePreviewContents(web_contents());
 }
 
 BackgroundPrintingManager::BackgroundPrintingManager() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 }
 
 BackgroundPrintingManager::~BackgroundPrintingManager() {
   DCHECK(CalledOnValidThread());
   // The might be some WebContentses still in |printing_contents_map_| at this
   // point (e.g. when the last remaining tab closes and there is still a print
@@ skipping 67 matching lines @@
   }
   return result;
 }
 
 bool BackgroundPrintingManager::HasPrintPreviewDialog(
     WebContents* preview_dialog) {
   return ContainsKey(printing_contents_map_, preview_dialog);
 }
 
 }  // namespace printing