PPAPI: Force async callback invocation option.

ppapi/cpp/private/flash_menu.cc

 // 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.
 
 // TODO(viettrungluu): See the comment in corresponding .h file.
 
 #include "ppapi/cpp/private/flash_menu.h"
 
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/cpp/completion_callback.h"
@@ skipping 18 matching lines @@
   if (has_interface<PPB_Flash_Menu>()) {
     PassRefFromConstructor(get_interface<PPB_Flash_Menu>()->Create(
         instance.pp_instance(), menu_data));
   }
 }
 
 int32_t Menu::Show(const Point& location,
                    int32_t* selected_id,
                    const CompletionCallback& cc) {
   if (!has_interface<PPB_Flash_Menu>())
-    return PP_ERROR_NOINTERFACE;
+    return cc.MayForce(PP_ERROR_NOINTERFACE);
   return get_interface<PPB_Flash_Menu>()->Show(
       pp_resource(),
       &location.pp_point(),
       selected_id,
       cc.pp_completion_callback());
 }
 
 }  // namespace flash
 }  // namespace pp