Remove remaining calls to deprecated MessageLoop methods on Mac.

chrome/browser/ui/cocoa/importer/import_lock_dialog_cocoa.mm

 // Copyright (c) 2011 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 <Cocoa/Cocoa.h>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/mac/scoped_nsobject.h"
-#include "base/message_loop/message_loop.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "chrome/browser/importer/importer_lock_dialog.h"
 #include "chrome/grit/chromium_strings.h"
 #include "chrome/grit/generated_resources.h"
 #include "content/public/browser/user_metrics.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 
 using base::UserMetricsAction;
 
 namespace importer {
 
 void ShowImportLockDialog(gfx::NativeWindow parent,
                           const base::Callback<void(bool)>& callback) {
   base::scoped_nsobject<NSAlert> lock_alert([[NSAlert alloc] init]);
   [lock_alert addButtonWithTitle:l10n_util::GetNSStringWithFixup(
       IDS_IMPORTER_LOCK_OK)];
   [lock_alert addButtonWithTitle:l10n_util::GetNSStringWithFixup(
       IDS_IMPORTER_LOCK_CANCEL)];
   [lock_alert setInformativeText:l10n_util::GetNSStringWithFixup(
       IDS_IMPORTER_LOCK_TEXT)];
   [lock_alert setMessageText:l10n_util::GetNSStringWithFixup(
       IDS_IMPORTER_LOCK_TITLE)];
 
-  base::MessageLoop::current()->PostTask(
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
       base::Bind(callback, [lock_alert runModal] == NSAlertFirstButtonReturn));
   content::RecordAction(UserMetricsAction("ImportLockDialogCocoa_Shown"));
 }
 
 }  // namespace importer