Add InputEventTimestampSource interface.

remoting/protocol/input_event_timestamps.h

+// Copyright 2016 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_INPUT_EVENT_TIMESTAMPS_H_
+#define REMOTING_PROTOCOL_INPUT_EVENT_TIMESTAMPS_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/time/time.h"
+
+namespace remoting {
+namespace protocol {
+
+// Used on the host side to track timestamps for input events.
+struct InputEventTimestamps {
+  // Client-side timestamps. This value comes from the client clock, so it
+  // should not be used for any calculations on the host side (except in tests).
+  base::TimeTicks client_timestamp;
+
+  // Time when the event was processed by the host.
+  base::TimeTicks host_timestamp;
+
+  bool is_null() { return client_timestamp.is_null(); }
+};
+
+// InputEventTimestampsSource is used by VideoStream implementations to get
+// event timestamps that are sent back to the client as part of VideoStats
+// message.
+class InputEventTimestampsSource
+    : public base::RefCountedThreadSafe<InputEventTimestampsSource> {
+ public:
+  InputEventTimestampsSource() {}
+
+  // Returns event timestamps for the input event that was received since the
+  // previous call. Null InputEventTimestamps value is returned if no input
+  // events were received. If multiple input events were received, then
+  // timestamps for the last one should be returned
+  virtual InputEventTimestamps TakeLastEventTimestamps() = 0;
+
+ protected:
+  friend base::RefCountedThreadSafe<InputEventTimestampsSource>;
+  virtual ~InputEventTimestampsSource() {}
+};
+
+// Simple implementations of InputEventTimestampsSource that just stores the
+// value provided to OnEventReceived().
+class InputEventTimestampsSourceImpl : public InputEventTimestampsSource {
+ public:
+  InputEventTimestampsSourceImpl();
+
+  void OnEventReceived(InputEventTimestamps timestamps);
+
+  // InputEventTimestampsSource implementation.
+  InputEventTimestamps TakeLastEventTimestamps() override;
+
+ protected:
+  ~InputEventTimestampsSourceImpl() override;
+
+ private:
+  InputEventTimestamps last_timestamps_;
+};
+
+}  // namespace protocol
+}  // namespace remoting
+
+#endif  // REMOTING_PROTOCOL_INPUT_EVENT_TIMESTAMPS_H_