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

chrome/plugin/npobject_proxy.h

 // Copyright (c) 2006-2008 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.
 //
 // A proxy for NPObject that sends all calls to the object to an NPObjectStub
 // running in a different process.
 
 #ifndef CHROME_PLUGIN_NPOBJECT_PROXY_H_
 #define CHROME_PLUGIN_NPOBJECT_PROXY_H_
 #pragma once
@@ skipping 21 matching lines @@
                       public NPObjectBase {
  public:
   ~NPObjectProxy();
 
   static NPObject* Create(PluginChannelBase* channel,
                           int route_id,
                           gfx::NativeViewId containing_window,
                           const GURL& page_url);
 
   // IPC::Message::Sender implementation:
-  bool Send(IPC::Message* msg);
+  virtual bool Send(IPC::Message* msg);
   int route_id() { return route_id_; }
   PluginChannelBase* channel() { return channel_; }
 
   // The next 9 functions are called on NPObjects from the plugin and browser.
   static bool NPHasMethod(NPObject *obj,
                           NPIdentifier name);
   static bool NPInvoke(NPObject *obj,
                        NPIdentifier name,
                        const NPVariant *args,
                        uint32_t arg_count,
@@ skipping 31 matching lines @@
                               bool is_default,
                               NPIdentifier name,
                               const NPVariant *args,
                               uint32_t arg_count,
                               NPVariant *result);
 
   static NPObjectProxy* GetProxy(NPObject* object);
   static const NPClass* npclass() { return &npclass_proxy_; }
 
   // NPObjectBase implementation.
-  virtual NPObject* GetUnderlyingNPObject() {
-    return NULL;
-  }
+  virtual NPObject* GetUnderlyingNPObject();
 
-  IPC::Channel::Listener* GetChannelListener() {
-    return static_cast<IPC::Channel::Listener*>(this);
-  }
+  virtual IPC::Channel::Listener* GetChannelListener();
 
  private:
   NPObjectProxy(PluginChannelBase* channel,
                 int route_id,
                 gfx::NativeViewId containing_window,
                 const GURL& page_url);
 
   // IPC::Channel::Listener implementation:
-  void OnMessageReceived(const IPC::Message& msg);
-  void OnChannelError();
+  virtual void OnMessageReceived(const IPC::Message& msg);
+  virtual void OnChannelError();
 
   static NPObject* NPAllocate(NPP, NPClass*);
   static void NPDeallocate(NPObject* npObj);
 
   // This function is only caled on NPObjects from the plugin.
   static void NPPInvalidate(NPObject *obj);
   static NPClass npclass_proxy_;
 
   scoped_refptr<PluginChannelBase> channel_;
   int route_id_;
   gfx::NativeViewId containing_window_;
 
   // The url of the main frame hosting the plugin.
   GURL page_url_;
 };
 
 #endif  // CHROME_PLUGIN_NPOBJECT_PROXY_H_