Chrome OS multi-profiles backend and UI.

chrome/browser/resources/chromeos/login/header_bar.js

Index: chrome/browser/resources/chromeos/login/header_bar.js
diff --git a/chrome/browser/resources/chromeos/login/header_bar.js b/chrome/browser/resources/chromeos/login/header_bar.js
index 0189220e74d9502f3332f32d5798091d4b05713d..85aff7239d655b7eefb6373a2ff4615825352369 100644
--- a/chrome/browser/resources/chromeos/login/header_bar.js
+++ b/chrome/browser/resources/chromeos/login/header_bar.js
@@ -179,15 +179,18 @@ cr.define('login', function() {
           (this.signinUIState_ == SIGNIN_UI_STATE.MANAGED_USER_CREATION_FLOW);
       var wrongHWIDWarningIsActive =
           (this.signinUIState_ == SIGNIN_UI_STATE.WRONG_HWID_WARNING);
+      var isMultiProfilesUI = Oobe.getInstance().isSignInToAddScreen();
 
-      $('add-user-button').hidden = !accountPickerIsActive;
+      $('add-user-button').hidden = !accountPickerIsActive || isMultiProfilesUI;
       $('cancel-add-user-button').hidden = accountPickerIsActive ||
           !this.allowCancel_ ||
-          wrongHWIDWarningIsActive;
+          wrongHWIDWarningIsActive ||
+          isMultiProfilesUI;
       $('guest-user-header-bar-item').hidden = gaiaIsActive ||
           managedUserCreationDialogIsActive ||
           !this.showGuest_ ||
-          wrongHWIDWarningIsActive;
+          wrongHWIDWarningIsActive ||
+          isMultiProfilesUI;
       $('add-user-header-bar-item').hidden =
           $('add-user-button').hidden && $('cancel-add-user-button').hidden;
       $('apps-header-bar-item').hidden = !this.hasApps_ ||