Add support for threadsafe completion callback factory.

ppapi/proxy/proxy_non_thread_safe_ref_count.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_PROXY_PROXY_NON_THREAD_SAFE_REF_COUNT_H_
-#define PPAPI_PROXY_PROXY_NON_THREAD_SAFE_REF_COUNT_H_
-
-#include "base/message_loop.h"
-#include "ppapi/cpp/completion_callback.h"
-
-namespace ppapi {
-namespace proxy {
-
-// This class is just like ppapi/cpp/non_thread_safe_ref_count.h but rather
-// than using pp::Module::core (which doesn't exist), it uses Chrome threads
-// which do.
-class ProxyNonThreadSafeRefCount {
- public:
-  ProxyNonThreadSafeRefCount() : ref_(0) {
-#ifndef NDEBUG
-    message_loop_ = MessageLoop::current();
-#endif
-  }
-
-  ~ProxyNonThreadSafeRefCount() {
-    PP_DCHECK(message_loop_ == MessageLoop::current());
-  }
-
-  int32_t AddRef() {
-    PP_DCHECK(message_loop_ == MessageLoop::current());
-    return ++ref_;
-  }
-
-  int32_t Release() {
-    PP_DCHECK(message_loop_ == MessageLoop::current());
-    return --ref_;
-  }
-
- private:
-  int32_t ref_;
-#ifndef NDEBUG
-  MessageLoop* message_loop_;
-#endif
-};
-
-}  // namespace proxy
-}  // namespace ppapi
-
-#endif  // PPAPI_PROXY_PROXY_NON_THREAD_SAFE_REF_COUNT_H_