Prevent the Online Reauth window from opening twice.

chrome/browser/ui/cocoa/profiles/user_manager_mac.mm

 // 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 "chrome/browser/ui/cocoa/profiles/user_manager_mac.h"
 
 #include "base/mac/foundation_util.h"
 #include "chrome/app/chrome_command_ids.h"
 #import "chrome/browser/app_controller_mac.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 347 matching lines @@
   return [[self window] isVisible];
 }
 
 - (void)windowWillClose:(NSNotification*)notification {
   [[NSNotificationCenter defaultCenter] removeObserver:self];
   DCHECK(userManagerObserver_);
   userManagerObserver_->WindowWasClosed();
 }
 
 - (void)showReauthDialogWithProfile:(Profile*)profile email:(std::string)email {
-  reauth_window_controller_.reset(
-      [[ReauthDialogWindowController alloc]
-          initWithProfile:profile
-                    email:email
-              webContents:webContents_.get()]);
+  if (!reauth_window_controller_) {
+    reauth_window_controller_.reset(
+        [[ReauthDialogWindowController alloc]
+            initWithProfile:profile
+                      email:email
+                webContents:webContents_.get()]);
+  }
 }
 
 - (void)closeReauthDialog {
-  [reauth_window_controller_ close];
+  reauth_window_controller_.reset();
 }
 
 @end
 
 
 // static
 void UserManager::Show(
     const base::FilePath& profile_path_to_focus,
     profiles::UserManagerTutorialMode tutorial_mode,
     profiles::UserManagerProfileSelected profile_open_action) {
@@ skipping 85 matching lines @@
   ProfileMetrics::LogTimeToOpenUserManager(
       base::Time::Now() - user_manager_started_showing_);
   user_manager_started_showing_ = base::Time();
 }
 
 void UserManagerMac::WindowWasClosed() {
   CloseReauthDialog();
   instance_ = NULL;
   delete this;
 }