Add virtual destructors for the Pepper API thunks.

ppapi/thunk/ppb_cursor_control_api.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.
 
 #ifndef PPAPI_THUNK_CURSOR_CONTROL_API_H_
 #define PPAPI_THUNK_CURSOR_CONTROL_API_H_
 
 #include "ppapi/c/dev/ppb_cursor_control_dev.h"
 #include "ppapi/proxy/interface_id.h"
 
 namespace ppapi {
 namespace thunk {
 
 class PPB_CursorControl_FunctionAPI {
  public:
-  static const ::pp::proxy::InterfaceID interface_id =
-      ::pp::proxy::INTERFACE_ID_PPB_CURSORCONTROL;
+  virtual ~PPB_CursorControl_FunctionAPI() {}
 
   virtual PP_Bool SetCursor(PP_Instance instance,
                             PP_CursorType_Dev type,
                             PP_Resource custom_image_id,
                             const PP_Point* hot_spot) = 0;
   virtual PP_Bool LockCursor(PP_Instance instance) = 0;
   virtual PP_Bool UnlockCursor(PP_Instance instance) = 0;
   virtual PP_Bool HasCursorLock(PP_Instance instance) = 0;
   virtual PP_Bool CanLockCursor(PP_Instance instance) = 0;
+
+  static const ::pp::proxy::InterfaceID interface_id =
+      ::pp::proxy::INTERFACE_ID_PPB_CURSORCONTROL;
+
 };
 
 }  // namespace thunk
 }  // namespace ppapi
 
 #endif  // PPAPI_THUNK_CURSOR_CONTROL_API_H_