Remove the #enable-fast-user-switcher flag.

components/signin/core/common/profile_management_switches.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.
 
 // These are functions to access various profile-management flags but with
 // possible overrides from Experiements.  This is done inside chrome/common
 // because it is accessed by files through the chrome/ directory tree.
 
 #ifndef CHROME_COMMON_PROFILE_MANAGEMENT_SWITCHES_H_
 #define CHROME_COMMON_PROFILE_MANAGEMENT_SWITCHES_H_
 
 namespace base {
 class CommandLine;
 }
 
 namespace switches {
 
 // Checks whether account consistency is enabled. If enabled, the account
 // management UI is available in the avatar bubble.
 bool IsEnableAccountConsistency();
 
 // Checks whether the webview-based sign in flow is enabled on Chrome desktop.
 bool IsEnableWebviewBasedSignin();
 
 // Whether the chrome.identity API should be multi-account.
 bool IsExtensionsMultiAccount();
 
-// Checks whether the flag for fast user switching is enabled.
-bool IsFastUserSwitching();
-
 // Enables using GAIA information to populate profile name and icon.
 bool IsGoogleProfileInfo();
 
 // Whether the new avatar menu is enabled, either because new profile management
 // is enabled or because the new profile management preview UI is enabled.
 bool IsNewAvatarMenu();
 
 // Use new profile management system, including profile sign-out and new
 // choosers.
 bool IsNewProfileManagement();
 
 // Whether the new profile management preview has been enabled.
 bool IsNewProfileManagementPreviewEnabled();
 
 // Called in tests to force enabling different modes.
 void EnableNewAvatarMenuForTesting(base::CommandLine* command_line);
 void DisableNewAvatarMenuForTesting(base::CommandLine* command_line);
 void EnableNewProfileManagementForTesting(base::CommandLine* command_line);
 void EnableAccountConsistencyForTesting(base::CommandLine* command_line);
 
 }  // namespace switches
 
 #endif  // CHROME_COMMON_PROFILE_MANAGEMENT_SWITCHES_H_