Add InputEventTimestampSource interface.

remoting/protocol/host_event_dispatcher.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 REMOTING_PROTOCOL_HOST_EVENT_DISPATCHER_H_
 #define REMOTING_PROTOCOL_HOST_EVENT_DISPATCHER_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
 #include "remoting/protocol/channel_dispatcher_base.h"
+#include "remoting/protocol/input_event_timestamps.h"
 
 namespace remoting {
 namespace protocol {
 
 class EventMessage;
 class InputStub;
 
 // HostEventDispatcher dispatches incoming messages on the event
 // channel to InputStub.
 class HostEventDispatcher : public ChannelDispatcherBase {
  public:
-  typedef base::Callback<void(int64_t)> OnInputEventCallback;
-
   HostEventDispatcher();
   ~HostEventDispatcher() override;
 
   // Set InputStub that will be called for each incoming input
   // message. Doesn't take ownership of |input_stub|. It must outlive
   // the dispatcher.
   void set_input_stub(InputStub* input_stub) { input_stub_ = input_stub; }
 
-  // Set callback to notify of each message's sequence number. The
-  // callback cannot tear down this object.
-  void set_on_input_event_callback(const OnInputEventCallback& value) {
-    on_input_event_callback_ = value;
-  }
+  scoped_refptr<InputEventTimestampSource> GetEventTimestampSource();
 
  private:
   void OnIncomingMessage(std::unique_ptr<CompoundBuffer> buffer) override;
 
+  scoped_refptr<InputEventTimestampSourceImpl> event_timestamp_source_;
+
   InputStub* input_stub_ = nullptr;
-  OnInputEventCallback on_input_event_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(HostEventDispatcher);
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_HOST_EVENT_DISPATCHER_H_