Control easy unlock by a field trial.

chrome/browser/signin/easy_unlock.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_H_
 #define CHROME_BROWSER_SIGNIN_EASY_UNLOCK_H_
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 class Profile;
 
 namespace easy_unlock {
 
 // Registers Easy Unlock profile preferences.
 void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
 // Launches Easy Unlock Setup app.
 void LaunchEasyUnlockSetup(Profile* profile);
 
+// Whether easy unlock is enabled. The feature is enabled when either the
+// flag is enabled or its field trial is enabled.
+bool IsEnabled();
+
 }  // namespace easy_unlock
 
 #endif  // CHROME_BROWSER_SIGNIN_EASY_UNLOCK_H_