Virtual destructors should have virtual keyword.

content/browser/plugin_service.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.
 
 // This class responds to requests from renderers for the list of plugins, and
 // also a proxy object for plugin instances.
 
 #ifndef CONTENT_BROWSER_PLUGIN_SERVICE_H_
 #define CONTENT_BROWSER_PLUGIN_SERVICE_H_
 #pragma once
@@ skipping 106 matching lines @@
   // list, and optionally also reload all the pages with plugins.
   // NOTE: can only be called on the UI thread.
   static void PurgePluginListCache(bool reload_pages);
 
  private:
   friend struct DefaultSingletonTraits<PluginService>;
 
   // Creates the PluginService object, but doesn't actually build the plugin
   // list yet.  It's generated lazily.
   PluginService();
-  ~PluginService();
+  virtual ~PluginService();
 
   // base::WaitableEventWatcher::Delegate implementation.
   virtual void OnWaitableEventSignaled(base::WaitableEvent* waitable_event);
 
   // NotificationObserver implementation
   virtual void Observe(NotificationType type, const NotificationSource& source,
                        const NotificationDetails& details);
 
   void RegisterPepperPlugins();
 
@@ skipping 50 matching lines @@
 
   std::vector<OverriddenPlugin> overridden_plugins_;
   base::Lock overridden_plugins_lock_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginService);
 };
 
 DISABLE_RUNNABLE_METHOD_REFCOUNT(PluginService);
 
 #endif  // CONTENT_BROWSER_PLUGIN_SERVICE_H_