Virtual destructors should have virtual keyword.

content/plugin/plugin_thread.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 CONTENT_PLUGIN_PLUGIN_THREAD_H_
 #define CONTENT_PLUGIN_PLUGIN_THREAD_H_
 #pragma once
 
 #include "base/file_path.h"
 #include "base/native_library.h"
 #include "build/build_config.h"
 #include "content/common/child_thread.h"
 #include "content/plugin/plugin_channel.h"
 #include "webkit/plugins/npapi/plugin_lib.h"
 
 #if defined(OS_POSIX)
 #include "base/file_descriptor_posix.h"
 #endif
 
 // The PluginThread class represents a background thread where plugin instances
 // live.  Communication occurs between WebPluginDelegateProxy in the renderer
 // process and WebPluginDelegateStub in this thread through IPC messages.
 class PluginThread : public ChildThread {
  public:
   PluginThread();
-  ~PluginThread();
+  virtual ~PluginThread();
 
   // Returns the one plugin thread.
   static PluginThread* current();
 
   FilePath plugin_path() { return plugin_path_; }
 
  private:
   virtual bool OnControlMessageReceived(const IPC::Message& msg);
 
   // Callback for when a channel has been created.
   void OnCreateChannel(int renderer_id, bool incognito);
   void OnPluginMessage(const std::vector<uint8> &data);
   void OnNotifyRenderersOfPendingShutdown();
 #if defined(OS_MACOSX)
   void OnAppActivated();
   void OnPluginFocusNotify(uint32 instance_id);
 #endif
 
   // The plugin module which is preloaded in Init
   base::NativeLibrary preloaded_plugin_module_;
 
   // Points to the plugin file that this process hosts.
   FilePath plugin_path_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginThread);
 };
 
 #endif  // CONTENT_PLUGIN_PLUGIN_THREAD_H_