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

chrome/browser/worker_host/message_port_dispatcher.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_WORKER_HOST_MESSAGE_PORT_DISPATCHER_H_
 #define CHROME_BROWSER_WORKER_HOST_MESSAGE_PORT_DISPATCHER_H_
 #pragma once
 
 #include <map>
 #include <utility>
@@ skipping 48 matching lines @@
                      const std::vector<int>& sent_message_port_ids);
   void OnQueueMessages(int message_port_id);
   void OnSendQueuedMessages(int message_port_id,
                             const QueuedMessages& queued_messages);
 
   void PostMessageTo(int message_port_id,
                      const string16& message,
                      const std::vector<int>& sent_message_port_ids);
 
   // NotificationObserver interface.
-  void Observe(NotificationType type,
-               const NotificationSource& source,
-               const NotificationDetails& details);
+  virtual void Observe(NotificationType type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details);
 
   // Handles the details of removing a message port id. Before calling this,
   // verify that the message port id exists.
   void Erase(int message_port_id);
 
   struct MessagePort;
   typedef std::map<int, MessagePort> MessagePorts;
   MessagePorts message_ports_;
 
   // We need globally unique identifiers for each message port.
   int next_message_port_id_;
 
   // Valid only during IPC message dispatching.
   IPC::Message::Sender* sender_;
   CallbackWithReturnValue<int>::Type* next_routing_id_;
 
   NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(MessagePortDispatcher);
 };
 
 #endif  // CHROME_BROWSER_WORKER_HOST_MESSAGE_PORT_DISPATCHER_H_