Virtual destructors should have virtual keyword.

webkit/plugins/npapi/test/plugin_npobject_lifetime_test.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 WEBKIT_PLUGINS_NPAPI_TEST_PLUGIN_NPOBJECT_LIFETIME_TEST_H_
 #define WEBKIT_PLUGINS_NPAPI_TEST_PLUGIN_NPOBJECT_LIFETIME_TEST_H_
 
 #include "build/build_config.h"
 #include "webkit/plugins/npapi/test/plugin_test.h"
 
@@ skipping 23 matching lines @@
 #endif
   DISALLOW_IMPLICIT_CONSTRUCTORS(NPObjectLifetimeTest);
 };
 
 // The NPObjectLifetimeTestInstance2 class represents the plugin instance
 // which is deleted by the NPObjectLifeTime class via a javascript function.
 class NPObjectLifetimeTestInstance2 : public PluginTest {
  public:
   // Constructor.
   NPObjectLifetimeTestInstance2(NPP id, NPNetscapeFuncs *host_functions);
-  ~NPObjectLifetimeTestInstance2();
+  virtual ~NPObjectLifetimeTestInstance2();
 
   // NPAPI SetWindow handler.
   virtual NPError SetWindow(NPWindow* pNPWindow);
  protected:
   static NPObject* plugin_instance_object_;
   friend class NPObjectLifetimeTest;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(NPObjectLifetimeTestInstance2);
 };
 
 // The NPObjectLifeTime class tests the case where a plugin instance is
 // destroyed in NPN_Evaluate
 class NPObjectDeletePluginInNPN_Evaluate : public PluginTest {
  public:
   // Constructor.
   NPObjectDeletePluginInNPN_Evaluate(NPP id, NPNetscapeFuncs *host_functions);
-  ~NPObjectDeletePluginInNPN_Evaluate();
+  virtual ~NPObjectDeletePluginInNPN_Evaluate();
 
   // NPAPI SetWindow handler.
   virtual NPError SetWindow(NPWindow* pNPWindow);
 
  protected:
   NPObject* plugin_instance_object_;
 #if defined(OS_WIN)
   static void CALLBACK TimerProc(HWND window, UINT message, UINT timer_id,
                                  unsigned long elapsed_milli_seconds);
   UINT_PTR timer_id_;
 #endif
 
  private:
   static NPObjectDeletePluginInNPN_Evaluate* g_npn_evaluate_test_instance_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(NPObjectDeletePluginInNPN_Evaluate);
 };
 
 }  // namespace NPAPIClient
 
 #endif  // WEBKIT_PLUGINS_NPAPI_TEST_PLUGIN_NPOBJECT_LIFETIME_TEST_H_