Don't make classes derive from ChildProcessHost, and instead have them use it through composition...

content/browser/plugin_process_host.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_BROWSER_PLUGIN_PROCESS_HOST_H_
 #define CONTENT_BROWSER_PLUGIN_PROCESS_HOST_H_
 #pragma once
 
 #include "build/build_config.h"
 
 #include <list>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "content/browser/browser_child_process_host.h"
 #include "content/common/content_export.h"
+#include "ipc/ipc_channel_proxy.h"
 #include "webkit/plugins/webplugininfo.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace content {
 class ResourceContext;
 }
 
 namespace gfx {
 class Rect;
 }
@@ skipping 32 matching lines @@
   };
 
   PluginProcessHost();
   virtual ~PluginProcessHost();
 
   // Initialize the new plugin process, returning true on success. This must
   // be called before the object can be used.
   bool Init(const webkit::WebPluginInfo& info, const std::string& locale);
 
   // Force the plugin process to shutdown (cleanly).
-  virtual void ForceShutdown() OVERRIDE;
+  void ForceShutdown();
 
   virtual bool OnMessageReceived(const IPC::Message& msg) OVERRIDE;
   virtual void OnChannelConnected(int32 peer_pid) OVERRIDE;
   virtual void OnChannelError() OVERRIDE;
 
   // Tells the plugin process to create a new channel for communication with a
   // renderer.  When the plugin process responds with the channel name,
   // OnChannelOpened in the client is called.
   void OpenChannelToPlugin(Client* client);
 
@@ skipping 19 matching lines @@
   void OnAppActivation();
 #endif
 
   const webkit::WebPluginInfo& info() const { return info_; }
 
 #if defined(OS_WIN)
   // Tracks plugin parent windows created on the browser UI thread.
   void AddWindow(HWND window);
 #endif
 
+  // Adds an IPC message filter.  A reference will be kept to the filter.
+  void AddFilter(IPC::ChannelProxy::MessageFilter* filter);
+
  private:
   // Sends a message to the plugin process to request creation of a new channel
   // for the given mime type.
   void RequestPluginChannel(Client* client);
 
   // Message handlers.
   void OnChannelCreated(const IPC::ChannelHandle& channel_handle);
 
 #if defined(OS_WIN)
   void OnPluginWindowDestroyed(HWND window, HWND parent);
@@ skipping 40 matching lines @@
   // Tracks modal windows currently visible.
   std::set<uint32> plugin_modal_windows_set_;
   // Tracks the current visibility of the cursor.
   bool plugin_cursor_visible_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(PluginProcessHost);
 };
 
 #endif  // CONTENT_BROWSER_PLUGIN_PROCESS_HOST_H_