Fix a crash where the ResourceMessageFilter is deleted

chrome/browser/extensions/extension_message_service.h

 // Copyright (c) 2009 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_SERVICE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_SERVICE_H_
 
 #include <map>
 #include <string>
 
 #include "base/lock.h"
+#include "chrome/common/notification_observer.h"
 
 class ExtensionView;
 class ResourceMessageFilter;
 class URLRequestContext;
 
 // This class manages message passing between renderer processes.  It maintains
 // a list of available extensions and which renderers each lives in, as well as
 // a set of open channels.
 //
 // Terminology:
 // channel: connection between two ports (one of which belongs to an extension)
 // port: an IPC::Message::Sender interface through which we communicate to a
 //   process.  We use MessageFilters for this since that allows us to send our
 //   messages on the IO thread.
-class ExtensionMessageService {
+class ExtensionMessageService : public NotificationObserver {
  public:
   // Returns the message service for the given context.  Messages can only
   // be sent within a single context.
   static ExtensionMessageService* GetInstance(URLRequestContext* context);
 
   ExtensionMessageService();
 
   // --- UI thread only:
 
   // Register an extension and its corresponding renderer process.
@@ skipping 10 matching lines @@
 
   // Sends a message from a renderer to the given port.
   void PostMessageFromRenderer(int port_id, const std::string& message,
                                ResourceMessageFilter* source);
 
   // --- UI or IO thread:
 
   // Called to let us know that a renderer has been started.
   void RendererReady(ResourceMessageFilter* port);
 
-  // Called to let us know that a renderer is going away.
-  void RendererShutdown(ResourceMessageFilter* port);
+  // NotificationObserver interface.
+  void Observe(NotificationType type,
+               const NotificationSource& source,
+               const NotificationDetails& details);
 
  private:
   // A map of extension ID to the render_process_id that the extension lives in.
   typedef std::map<std::string, int> ProcessIDMap;
   ProcessIDMap process_ids_;
 
   // A map of render_process_id to its corresponding message filter, which we
   // use for sending messages.
   typedef std::map<int, ResourceMessageFilter*> RendererMap;
   RendererMap renderers_;
@@ skipping 13 matching lines @@
 
   // A map of channel ID to its channel object.
   typedef std::map<int, MessageChannel> MessageChannelMap;
   MessageChannelMap channels_;
 
   // For generating unique channel IDs.
   int next_port_id_;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_SERVICE_H_