Add the "virtual" keyword on method overrides that are missing it.

chrome/renderer/webplugin_delegate_proxy.h

 // Copyright (c) 2010 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_RENDERER_WEBPLUGIN_DELEGATE_PROXY_H_
 #define CHROME_RENDERER_WEBPLUGIN_DELEGATE_PROXY_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 76 matching lines @@
   // Informs the plugin that its container (window/tab) has changed visibility.
   virtual void SetContainerVisibility(bool is_visible);
   // Informs the plugin that its enclosing window's frame has changed.
   virtual void WindowFrameChanged(gfx::Rect window_frame, gfx::Rect view_frame);
   // Informs the plugin that text is avaiable from plugin IME.
   virtual void ImeCompositionConfirmed(const string16& text, int plugin_id);
 #endif
 
   // IPC::Channel::Listener implementation:
   virtual void OnMessageReceived(const IPC::Message& msg);
-  void OnChannelError();
+  virtual void OnChannelError();
 
   // IPC::Message::Sender implementation:
   virtual bool Send(IPC::Message* msg);
 
   virtual void SendJavaScriptStream(const GURL& url,
                                     const std::string& result,
                                     bool success,
                                     int notify_id);
 
   virtual void DidReceiveManualResponse(const GURL& url,
@@ skipping 166 matching lines @@
   // This lets us know which portion of the backing store has been painted into.
   gfx::Rect backing_store_painted_;
 
   // The url of the main frame hosting the plugin.
   GURL page_url_;
 
   DISALLOW_COPY_AND_ASSIGN(WebPluginDelegateProxy);
 };
 
 #endif  // CHROME_RENDERER_WEBPLUGIN_DELEGATE_PROXY_H_