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

chrome/browser/plugin_updater.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_BROWSER_PLUGIN_UPDATER_H_
 #define CHROME_BROWSER_PLUGIN_UPDATER_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 23 matching lines @@
   // Enable or disable a specific plugin file.
   void EnablePluginFile(bool enable, const FilePath::StringType& file_path);
 
   // Disable all plugin groups as defined by the user's preference file.
   void DisablePluginGroupsFromPrefs(Profile* profile);
 
   // Write the enable/disable status to the user's preference file.
   void UpdatePreferences(Profile* profile, int delay_ms);
 
   // NotificationObserver method overrides
-  void Observe(NotificationType type,
-               const NotificationSource& source,
-               const NotificationDetails& details);
+  virtual void Observe(NotificationType type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details);
 
   static PluginUpdater* GetPluginUpdater();
 
  private:
   PluginUpdater();
   virtual ~PluginUpdater() {}
 
   // Called on the file thread to get the data necessary to update the saved
   // preferences.  The profile pointer is only to be passed to the UI thread.
   static void GetPreferencesDataOnFileThread(void* profile);
@@ skipping 23 matching lines @@
   // Note: if you change this to false from true, you must update
   // kPluginsEnabledInternalPDF to be a new name (i.e. add 2, 3, 4...) at end.
   bool enable_internal_pdf_;
 
   bool notify_pending_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginUpdater);
 };
 
 #endif  // CHROME_BROWSER_PLUGIN_UPDATER_H_