Remove remaining calls to deprecated MessageLoop methods on Mac.

chrome/browser/ui/cocoa/profiles/profile_signin_confirmation_dialog_cocoa.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.
 
 #import "chrome/browser/ui/cocoa/profiles/profile_signin_confirmation_dialog_cocoa.h"
 
-#include "base/message_loop/message_loop.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/browser_window.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_sheet.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_window.h"
 #include "chrome/browser/ui/sync/profile_signin_confirmation_helper.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 
 namespace {
 
@@ skipping 58 matching lines @@
       profile, base::Bind(ShowDialog, browser, web_contents, profile, username,
                           delegate));
 }
 
 void ProfileSigninConfirmationDialogCocoa::Close() {
   window_->CloseWebContentsModalDialog();
 }
 
 void ProfileSigninConfirmationDialogCocoa::OnConstrainedWindowClosed(
     ConstrainedWindowMac* window) {
-  base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
+  base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, this);
 }