cros: Add enterprise user session metrics

chrome/browser/chromeos/login/enterprise_user_session_metrics.h

+// Copyright 2017 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 CHROME_BROWSER_CHROMEOS_LOGIN_ENTERPRISE_USER_SESSION_METRICS_H_
+#define CHROME_BROWSER_CHROMEOS_LOGIN_ENTERPRISE_USER_SESSION_METRICS_H_
+
+#include "base/time/time.h"
+#include "components/user_manager/user_type.h"
+
+class PrefRegistrySimple;
+
+namespace chromeos {
+
+class UserContext;
+
+namespace enterprise_user_session_metrics {
+
+// Enum for logins metrics on an enrolled device.
+enum SignInEventType {

[achuithb, 2017/02/15 10:54:57]

enum class is preferred now I believe:
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/Q5WmkAImanc

[xiyuan, 2017/02/15 19:08:10]

Done.

+  // A regular user login.
+  REGULAR_USER = 0,
+  // Manually started public session.
+  MANUAL_PUBLIC_SESSION = 1,
+  // Automatically started public session.
+  AUTOMATIC_PUBLIC_SESSSION = 2,
+  // Manually started kiosk session.
+  MANUAL_KIOSK = 3,
+  // Automatically started kiosk session.
+  AUTOMATIC_KIOSK = 4,
+  // Count of sign-in event types. Must be the last one.
+  SIGN_IN_EVENT_COUNT,
+};
+
+// Register local state preferences.
+void RegisterPrefs(PrefRegistrySimple* registry);
+
+// Records a sign-in event for an enrolled device.
+void RecordSignInEvent(SignInEventType sign_in_event_type);
+
+// Records a sign-in event by UserContext for an enrolled device.

[achuithb, 2017/02/15 10:54:57]

Is is_auto_login well understood in this part of the codebase?

[xiyuan, 2017/02/15 19:08:10]

Added comment to document what |is_auto_login| represents.

+void RecordSignInEvent(const UserContext& user_context, bool is_auto_login);
+
+// Stores session length for regular user, public session user for enrolled
+// device to be reported on the next run. It stores the duration in a local
+// state pref instead of sending it to metrics code directly because it is
+// called on shutdown path and metrics are likely to lost. The stored value

[achuithb, 2017/02/15 10:54:57]

to be lost.

[xiyuan, 2017/02/15 19:08:10]

Done.

+// would be reported on the next run.
+void StoreSessionLength(user_manager::UserType session_type,
+                        const base::TimeDelta& session_length);
+
+// Records the stored session length and clears it.
+void RecordStoredSessionLength();
+
+}  // namespace enterprise_user_session_metrics
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_ENTERPRISE_USER_SESSION_METRICS_H_