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

components/signin/core/common/profile_management_switches.cc

 // 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.
 
 #include "components/signin/core/common/profile_management_switches.h"
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "build/build_config.h"
 #include "components/signin/core/common/signin_switches.h"
@@ skipping 119 matching lines @@
   return !base::CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kEnableIframeBasedSignin);
 #endif
 }
 
 bool IsExtensionsMultiAccount() {
   return CheckFlag(switches::kExtensionsMultiAccount,
                    STATE_ACCOUNT_CONSISTENCY);
 }
 
-bool IsFastUserSwitching() {
-  return base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kFastUserSwitching);
-}
-
 bool IsGoogleProfileInfo() {
   return CheckFlag(switches::kGoogleProfileInfo, STATE_NEW_AVATAR_MENU);
 }
 
 bool IsNewAvatarMenu() {
   // NewAvatarMenu is only available on desktop.
 #if defined(OS_ANDROID) || defined(OS_IOS) || defined(OS_CHROMEOS)
   return false;
 #else
   return GetProcessState() >= STATE_NEW_AVATAR_MENU;
@@ skipping 23 matching lines @@
   command_line->AppendSwitch(switches::kEnableNewProfileManagement);
   DCHECK(!command_line->HasSwitch(switches::kDisableNewProfileManagement));
 }
 
 void EnableAccountConsistencyForTesting(base::CommandLine* command_line) {
   command_line->AppendSwitch(switches::kEnableAccountConsistency);
   DCHECK(!command_line->HasSwitch(switches::kDisableAccountConsistency));
 }
 
 }  // namespace switches