Add InputEventTimestampSource interface.

remoting/protocol/input_event_timestamps.cc

+// 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.
+
+#include "remoting/protocol/input_event_timestamps.h"
+
+namespace remoting {
+namespace protocol {
+
+InputEventTimestampsSourceImpl::InputEventTimestampsSourceImpl() {}
+InputEventTimestampsSourceImpl::~InputEventTimestampsSourceImpl() {}
+
+void InputEventTimestampsSourceImpl::OnEventReceived(
+    InputEventTimestamps timestamps) {
+  last_timestamps_ = timestamps;
+}
+
+InputEventTimestamps InputEventTimestampsSourceImpl::TakeLastEventTimestamps() {
+  InputEventTimestamps result = last_timestamps_;
+  last_timestamps_ = InputEventTimestamps();
+  return result;
+}
+
+}  // namespace protocol
+}  // namespace remoting