Remove the sign-in menu item on macOS.

chrome/browser/app_controller_mac.h

 // Copyright (c) 2012 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_APP_CONTROLLER_MAC_H_
 #define CHROME_BROWSER_APP_CONTROLLER_MAC_H_
 
 #if defined(__OBJC__)
 
 #import <Cocoa/Cocoa.h>
@@ skipping 101 matching lines @@
   // This will be true after receiving a NSWorkspaceWillPowerOffNotification.
   BOOL isPoweringOff_;
 
   // Request to keep the browser alive during that object's lifetime.
   std::unique_ptr<ScopedKeepAlive> keep_alive_;
 }
 
 @property(readonly, nonatomic) BOOL startupComplete;
 @property(readonly, nonatomic) Profile* lastProfile;
 
-// Helper method used to update the "Signin" menu item in the main menu and the
-// wrench menu to reflect the current signed in state.
-+ (void)updateSigninItem:(id)signinItem
-              shouldShow:(BOOL)showSigninMenuItem
-          currentProfile:(Profile*)profile;
-
 - (void)didEndMainMessageLoop;
 
 // Try to close all browser windows, and if that succeeds then quit.
 - (BOOL)tryToTerminateApplication:(NSApplication*)app;
 
 // Stop trying to terminate the application. That is, prevent the final browser
 // window closure from causing the application to quit.
 - (void)stopTryingToTerminateApplication:(NSApplication*)app;
 
 // Indicate that the system is powering off or logging out.
@@ skipping 55 matching lines @@
 namespace app_controller_mac {
 
 // True if we are currently handling an IDC_NEW_{TAB,WINDOW} command. Used in
 // SessionService::Observe() to get around windows/linux and mac having
 // different models of application lifetime.
 bool IsOpeningNewWindow();
 
 }  // namespace app_controller_mac
 
 #endif