Remove remaining calls to deprecated MessageLoop methods on Mac.

ios/crnet/crnet_environment.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 "ios/crnet/crnet_environment.h"
 
 #import <Foundation/Foundation.h>
 
 #include <utility>
 
@@ skipping 121 matching lines @@
     return getter_.get();
   }
 
   scoped_refptr<net::URLRequestContextGetter> getter_;
   base::mac::ScopedBlock<RequestFilterBlock> filter_;
 };
 
 void CrNetEnvironment::PostToNetworkThread(
     const tracked_objects::Location& from_here,
     const base::Closure& task) {
-  network_io_thread_->message_loop()->PostTask(from_here, task);
+  network_io_thread_->task_runner()->PostTask(from_here, task);
 }
 
 void CrNetEnvironment::PostToFileUserBlockingThread(
     const tracked_objects::Location& from_here,
     const base::Closure& task) {
-  file_user_blocking_thread_->message_loop()->PostTask(from_here, task);
+  file_user_blocking_thread_->task_runner()->PostTask(from_here, task);
 }
 
 // static
 void CrNetEnvironment::Initialize() {
   DCHECK_EQ([NSThread currentThread], [NSThread mainThread]);
   if (!g_at_exit_)
     g_at_exit_ = new base::AtExitManager;
 
   // Change the framework bundle to the bundle that contain CrNet framework.
   // By default the framework bundle is set equal to the main (app) bundle.
@@ skipping 331 matching lines @@
 
   return user_agent_settings->GetUserAgent();
 }
 
 void CrNetEnvironment::ClearCache(ClearCacheCallback callback) {
   PostToNetworkThread(
       FROM_HERE,
       base::Bind(&net::ClearHttpCache, main_context_getter_,
                  network_io_thread_->task_runner(), base::BindBlock(callback)));
 }