Example of how to interpose yourself in a message stream.

content/common/child_thread.h

 // Copyright (c) 2011 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 CONTENT_COMMON_CHILD_THREAD_H_
 #define CONTENT_COMMON_CHILD_THREAD_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 24 matching lines @@
 
   // IPC::Message::Sender implementation:
   virtual bool Send(IPC::Message* msg);
 
   // See documentation on MessageRouter for AddRoute and RemoveRoute
   void AddRoute(int32 routing_id, IPC::Channel::Listener* listener);
   void RemoveRoute(int32 routing_id);
 
   IPC::Channel::Listener* ResolveRoute(int32 routing_id);
 
+  IPC::SyncChannel* channel() { return channel_.get(); }
+
   // Creates a ResourceLoaderBridge.
   // Tests can override this method if they want a custom loading behavior.
   virtual webkit_glue::ResourceLoaderBridge* CreateBridge(
       const webkit_glue::ResourceLoaderBridge::RequestInfo& request_info);
 
   ResourceDispatcher* resource_dispatcher();
 
   SocketStreamDispatcher* socket_stream_dispatcher() {
     return socket_stream_dispatcher_.get();
   }
@@ skipping 22 matching lines @@
   void OnProcessFinalRelease();
 
   virtual bool OnControlMessageReceived(const IPC::Message& msg);
   virtual void OnAskBeforeShutdown();
   virtual void OnShutdown();
 
 #ifdef IPC_MESSAGE_LOG_ENABLED
   virtual void OnSetIPCLoggingEnabled(bool enable);
 #endif
 
-  IPC::SyncChannel* channel() { return channel_.get(); }
-
   void set_on_channel_error_called(bool on_channel_error_called) {
     on_channel_error_called_ = on_channel_error_called;
   }
 
  private:
   void Init();
 
   // IPC::Channel::Listener implementation:
   virtual bool OnMessageReceived(const IPC::Message& msg);
   virtual void OnChannelError();
@@ skipping 27 matching lines @@
   scoped_ptr<NotificationService> notification_service_;
 
   scoped_ptr<FileSystemDispatcher> file_system_dispatcher_;
 
   scoped_ptr<QuotaDispatcher> quota_dispatcher_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildThread);
 };
 
 #endif  // CONTENT_COMMON_CHILD_THREAD_H_