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diff --git a/ppapi/proxy/callback_tracker.h b/ppapi/proxy/callback_tracker.h
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+++ b/ppapi/proxy/callback_tracker.h
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+// Copyright (c) 2010 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_CALLBACK_TRACKER_H_
+#define PPAPI_PROXY_CALLBACK_TRACKER_H_
+
+#include <map>
+
+#include "ppapi/c/pp_completion_callback.h"
+#include "ppapi/c/pp_stdint.h"
+
+namespace pp {
+namespace proxy {
+
+class Dispatcher;
+
+// This object tracks cross-process callbacks. When the plugin sends a callback
+// object to the renderer, we save the information and pass an identifier
+// instead.
+//
+// On the renderer side, this identifier is converted to a new callback in that
+// process. When executed, this new callback sends an IPC message containing the
+// previous identifier back to the plugin.
+//
+// When we receive that message, ExecuteSerializedCallback converts the
+// identifier back to the original callback information and runs the callback.
+class CallbackTracker {
+ public:
+  CallbackTracker(Dispatcher* dispatcher);
+  ~CallbackTracker();
+
+  // Converts the given callback in the context of the plugin to a serialized
+  // ID. This will be passed to ReceiveCallback on the renderer side.
+  uint32_t SendCallback(PP_CompletionCallback callback);
+
+  // Converts the given serialized callback ID to a new completion callback in
+  // the context of the current process. This callback actually will represent
+  // a proxy that will execute the callback in the plugin process.
+  PP_CompletionCallback ReceiveCallback(uint32_t serialized_callback);
+
+  // Sends a request to the remote process to execute the given callback.
+  void SendExecuteSerializedCallback(uint32_t serialized_callback,
+                                     int32_t param);
+
+  // Executes the given callback ID with the given result in the current
+  // process. This will also destroy the information associated with the
+  // callback and the serialized ID won't be valid any more.
+  void ReceiveExecuteSerializedCallback(uint32_t serialized_callback,
+                                        int32_t param);
+
+ private:
+  // Pointer to the dispatcher that owns us.
+  Dispatcher* dispatcher_;
+
+  int32_t next_callback_id_;
+
+  // Maps callback IDs to the actual callback objects in the plugin process.
+  typedef std::map<int32_t, PP_CompletionCallback> CallbackMap;
+  CallbackMap callback_map_;
+};
+
+}  // namespace proxy
+}  // namespace pp
+
+#endif  // PPAPI_PROXY_CALLBACK_TRACKER_H_