PPAPI: Make blocking completion callbacks work.

ppapi/thunk/ppb_audio_api.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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_AUDIO_API_H_
 #define PPAPI_THUNK_PPB_AUDIO_API_H_
 
+#include "base/memory/ref_counted.h"
 #include "ppapi/c/pp_completion_callback.h"
 #include "ppapi/c/ppb_audio.h"
 #include "ppapi/thunk/ppapi_thunk_export.h"
 
 namespace ppapi {
+
+class TrackedCallback;
+
 namespace thunk {
 
 class PPAPI_THUNK_EXPORT PPB_Audio_API {
  public:
   virtual ~PPB_Audio_API() {}
 
   virtual PP_Resource GetCurrentConfig() = 0;
   virtual PP_Bool StartPlayback() = 0;
   virtual PP_Bool StopPlayback() = 0;
 
   // Trusted API.
-  virtual int32_t OpenTrusted(PP_Resource config_id,
-                              PP_CompletionCallback create_callback) = 0;
+  virtual int32_t OpenTrusted(
+      PP_Resource config_id,
+      scoped_refptr<TrackedCallback> create_callback) = 0;
   virtual int32_t GetSyncSocket(int* sync_socket) = 0;
   virtual int32_t GetSharedMemory(int* shm_handle, uint32_t* shm_size) = 0;
 };
 
 }  // namespace thunk
 }  // namespace ppapi
 
 #endif  // PPAPI_THUNK_PPB_AUDIO_API_H_