[Smart Lock] Add UMA metrics to measure duration of unlock.

chrome/browser/signin/easy_unlock_service_signin_chromeos.h

 // Copyright 2014 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_SIGNIN_EASY_UNLOCK_SERVICE_SIGNIN_CHROMEOS_H_
 #define CHROME_BROWSER_SIGNIN_EASY_UNLOCK_SERVICE_SIGNIN_CHROMEOS_H_
 
 #include <map>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/time/time.h"
 #include "base/values.h"
 #include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_types.h"
 #include "chrome/browser/signin/easy_unlock_service.h"
 #include "chrome/browser/signin/screenlock_bridge.h"
 #include "chromeos/login/login_state.h"
 
 // EasyUnlockService instance that should be used for signin profile.
 class EasyUnlockServiceSignin : public EasyUnlockService,
                                 public ScreenlockBridge::Observer,
                                 public chromeos::LoginState::Observer {
@@ skipping 88 matching lines @@
   // Whether failed attempts to load user data should be retried.
   // This is to handle case where cryptohome daemon is not started in time the
   // service attempts to load some data. Retries will be allowed only until the
   // first data load finishes (even if it fails).
   bool allow_cryptohome_backoff_;
 
   // Whether the service has been successfully initialized, and has not been
   // shut down.
   bool service_active_;
 
+  // The timestamp for the most recent time when a user pod was focused.
+  base::TimeTicks user_pod_last_focused_timestamp_;
+
   base::WeakPtrFactory<EasyUnlockServiceSignin> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(EasyUnlockServiceSignin);
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_EASY_UNLOCK_SERVICE_SIGNIN_CHROMEOS_H_