Remove remaining calls to deprecated MessageLoop methods on Mac.

ios/chrome/browser/signin/browser_state_data_remover.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 "ios/chrome/browser/signin/browser_state_data_remover.h"
 
 #include "base/logging.h"
-#include "base/message_loop/message_loop.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "components/prefs/pref_service.h"
 #include "components/signin/core/common/signin_pref_names.h"
 #include "ios/chrome/browser/bookmarks/bookmarks_utils.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #import "ios/chrome/browser/ui/commands/UIKit+ChromeExecuteCommand.h"
 #import "ios/chrome/browser/ui/commands/clear_browsing_data_command.h"
 
 namespace {
 const int kRemoveAllDataMask = ~0;
 }
@@ skipping 43 matching lines @@
   }
 
   if (forget_last_username_) {
     browser_state_->GetPrefs()->ClearPref(prefs::kGoogleServicesLastAccountId);
     browser_state_->GetPrefs()->ClearPref(prefs::kGoogleServicesLastUsername);
   }
 
   if (callback_)
     callback_.get()();
 
-  base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
+  base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, this);
 }