Add virtual destructors for the Pepper API thunks.

ppapi/thunk/ppb_char_set_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_PPB_CHAR_SET_API_H_
 #define PPAPI_THUNK_PPB_CHAR_SET_API_H_
 
 #include "ppapi/c/dev/ppb_char_set_dev.h"
 #include "ppapi/proxy/interface_id.h"
 
 namespace ppapi {
 namespace thunk {
 
 class PPB_CharSet_FunctionAPI {
  public:
-  static const ::pp::proxy::InterfaceID interface_id =
-      ::pp::proxy::INTERFACE_ID_PPB_CHAR_SET;
+  virtual ~PPB_CharSet_FunctionAPI() {}
 
   virtual char* UTF16ToCharSet(PP_Instance instance,
                                const uint16_t* utf16, uint32_t utf16_len,
                                const char* output_char_set,
                                PP_CharSet_ConversionError on_error,
                                uint32_t* output_length) = 0;
   virtual uint16_t* CharSetToUTF16(PP_Instance instance,
                                    const char* input, uint32_t input_len,
                                    const char* input_char_set,
                                    PP_CharSet_ConversionError on_error,
                                    uint32_t* output_length) = 0;
   virtual PP_Var GetDefaultCharSet(PP_Instance instance) = 0;
+
+  static const ::pp::proxy::InterfaceID interface_id =
+      ::pp::proxy::INTERFACE_ID_PPB_CHAR_SET;
 };
 
 }  // namespace thunk
 }  // namespace ppapi
 
 #endif  // PPAPI_THUNK_CHAR_SET_API_H_