Add support for threadsafe completion callback factory.

ppapi/proxy/proxy_completion_callback_factory.h

+// 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_PROXY_PROXY_COMPLETION_CALLBACK_FACTORY_H_
+#define PPAPI_PROXY_PROXY_COMPLETION_CALLBACK_FACTORY_H_
+
+#include "base/message_loop.h"
+#include "ppapi/cpp/completion_callback.h"
+#include "ppapi/utility/completion_callback_factory.h"
+
+namespace ppapi {
+namespace proxy {
+
+// This class is just like pp::NonThreadSafeThreadTraits but rather than using
+// pp::Module::core (which doesn't exist), it uses Chrome threads which do.
+class ProxyNonThreadSafeThreadTraits {
+ public:
+  class RefCount {
+   public:
+    RefCount() : ref_(0) {
+#ifndef NDEBUG
+      message_loop_ = MessageLoop::current();
+#endif
+    }
+
+    ~RefCount() {
+      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_;

[viettrungluu, 2012/07/10 22:47:58]

What I said elsewhere about maybe dchecking ref > 0....

+    }
+
+   private:
+    int32_t ref_;
+#ifndef NDEBUG
+    MessageLoop* message_loop_;
+#endif
+  };
+
+  // No-op lock class.
+  class Lock {
+   public:
+    Lock() {}
+    ~Lock() {}
+
+    void Acquire() {}
+    void Release() {}
+  };
+
+  // No-op AutoLock class.
+  class AutoLock {
+   public:
+    explicit AutoLock(Lock&) {}
+    ~AutoLock() {}
+  };
+};
+
+template<typename T>
+class ProxyCompletionCallbackFactory
+    : public pp::CompletionCallbackFactory<T, ProxyNonThreadSafeThreadTraits> {
+ public:
+  ProxyCompletionCallbackFactory() : CompletionCallbackFactory() {}
+  ProxyCompletionCallbackFactory(T* t) : CompletionCallbackFactory(t) {}
+};
+
+}  // namespace proxy
+}  // namespace ppapi
+
+#endif  // PPAPI_PROXY_PROXY_COMPLETION_CALLBACK_FACTORY_H_