Added ConnectionTimeObserver to calculate the times to authenticate and connect.

remoting/test/connection_time_observer.h

+// Copyright 2015 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_TEST_CONNECTION_TIME_OBSERVER_H_
+#define REMOTING_TEST_CONNECTION_TIME_OBSERVER_H_
+
+#include <map>
+
+#include "remoting/test/remote_connection_observer.h"
+
+namespace base {
+class TimeDelta;
+}
+
+namespace remoting {
+namespace test {
+
+// Observes and saves the times when a chromoting client changes its state. It
+// allows for tests to access latency times between the different states the
+// client was in.

[joedow, 2015/07/24 13:38:28]

nit: s/was in/transitioned through

[tonychun, 2015/07/27 16:03:37]

Done.

+class ConnectionTimeObserver
+    : public RemoteConnectionObserver {
+ public:
+  ConnectionTimeObserver();
+  ~ConnectionTimeObserver() override;
+
+  // RemoteConnectionObserver interface.
+  void ConnectionStateChanged(protocol::ConnectionToHost::State state,
+                              protocol::ErrorCode error_code) override;

[joedow, 2015/07/24 13:38:28]

You may consider adding a helper method for setting the intial state (either
something like 'Start' if the usage is like a stopwatch or a simplified version
of this method so the caller doesn't need to provide an ErrorCode (since you
don't use it at the moment).

[tonychun, 2015/07/27 16:03:38]

Done.

+
+  // Prints out connection performance stats to STDOUT.
+  void DisplayConnectionStats();

[joedow, 2015/07/24 13:38:28]

this method should be const.

[tonychun, 2015/07/27 16:03:37]

Done.

+
+  // Returns the delta time in milliseconds between |start_state| and

[joedow, 2015/07/24 13:38:29]

nit: s/delta time/time delta

[tonychun, 2015/07/27 16:03:38]

Done.

+  // |end_state| stored in |transition_times_map_|.
+  base::TimeDelta GetStateTransitionDelay(

[joedow, 2015/07/24 13:38:28]

With the updated signature, this method should probably be called
GetStateTransitionDelayTimeDelta().  

[tonychun, 2015/07/27 16:03:37]

Done.

+      const protocol::ConnectionToHost::State& start_state,

[joedow, 2015/07/24 13:38:29]

The parameters here do not need to  be passed as const ref because they are
passed by value.  Please remove the const ref'ness for the enum values being
passed.

[tonychun, 2015/07/27 16:03:37]

Done.

+      const protocol::ConnectionToHost::State& end_state) const;
+
+  // Used to set fake state transition times for ConnectionTimeObserver tests.
+  void SetTransitionTimesMapForTest(
+      const std::map<protocol::ConnectionToHost::State, base::TimeTicks>& map);
+
+ private:
+  // Saves the current connection state of client to host.
+  protocol::ConnectionToHost::State current_connection_state_ =
+      protocol::ConnectionToHost::State::INITIALIZING;
+
+  // Stores TimeTick of states the client changes to.
+  std::map<protocol::ConnectionToHost::State, base::TimeTicks>
+      transition_times_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(ConnectionTimeObserver);
+};
+
+}  // namespace test
+}  // namespace remoting
+
+#endif  // REMOTING_TEST_CONNECTION_TIME_OBSERVER_H_