Revert of ios: Remove use of MessageLoopProxy and deprecated MessageLoop APIs

ios/web/web_thread_adapter.cc

 // 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 "ios/web/web_thread_adapter.h"
 
 #include "content/public/browser/browser_thread.h"
 
 namespace web {
 
@@ skipping 146 matching lines @@
 bool WebThread::GetCurrentThreadIdentifier(ID* identifier) {
   content::BrowserThread::ID content_identifier;
   bool result =
       content::BrowserThread::GetCurrentThreadIdentifier(&content_identifier);
   if (result)
     *identifier = WebThreadIDFromBrowserThreadID(content_identifier);
   return result;
 }
 
 // static
-scoped_refptr<base::SingleThreadTaskRunner> WebThread::GetTaskRunnerForThread(
+scoped_refptr<base::MessageLoopProxy> WebThread::GetMessageLoopProxyForThread(
     ID identifier) {
-  return content::BrowserThread::GetTaskRunnerForThread(
+  return content::BrowserThread::GetMessageLoopProxyForThread(
       BrowserThreadIDFromWebThreadID(identifier));
 }
 
 // static
 std::string WebThread::GetDCheckCurrentlyOnErrorMessage(ID expected) {
   return content::BrowserThread::GetDCheckCurrentlyOnErrorMessage(
       BrowserThreadIDFromWebThreadID(expected));
 }
 
 }  // namespace web