Encouraging ThreadTaskRunnerHandle usage in net/dns module

net/dns/serial_worker.cc

 // Copyright (c) 2012 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 "net/dns/serial_worker.h"
 
 #include "base/bind.h"
 #include "base/location.h"
-#include "base/message_loop/message_loop_proxy.h"
+#include "base/thread_task_runner_handle.h"
 #include "base/threading/worker_pool.h"
 
 namespace net {
 
 SerialWorker::SerialWorker()
-  : message_loop_(base::MessageLoopProxy::current()),
-    state_(IDLE) {}
+    : task_runner_(base::ThreadTaskRunnerHandle::Get()), state_(IDLE) {
+}
 
 SerialWorker::~SerialWorker() {}
 
 void SerialWorker::WorkNow() {
-  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(task_runner_->BelongsToCurrentThread());
   switch (state_) {
     case IDLE:
       if (!base::WorkerPool::PostTask(FROM_HERE, base::Bind(
           &SerialWorker::DoWorkJob, this), false)) {
 #if defined(OS_POSIX)
         // See worker_pool_posix.cc.
         NOTREACHED() << "WorkerPool::PostTask is not expected to fail on posix";
 #else
         LOG(WARNING) << "Failed to WorkerPool::PostTask, will retry later";
         const int kWorkerPoolRetryDelayMs = 100;
-        message_loop_->PostDelayedTask(
+        task_runner_->PostDelayedTask(
             FROM_HERE,
             base::Bind(&SerialWorker::RetryWork, this),
             base::TimeDelta::FromMilliseconds(kWorkerPoolRetryDelayMs));
         state_ = WAITING;
         return;
 #endif
       }
       state_ = WORKING;
       return;
     case WORKING:
       // Remember to re-read after |DoRead| finishes.
       state_ = PENDING;
       return;
     case CANCELLED:
     case PENDING:
     case WAITING:
       return;
     default:
       NOTREACHED() << "Unexpected state " << state_;
   }
 }
 
 void SerialWorker::Cancel() {
-  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(task_runner_->BelongsToCurrentThread());
   state_ = CANCELLED;
 }
 
 void SerialWorker::DoWorkJob() {
   this->DoWork();
   // If this fails, the loop is gone, so there is no point retrying.
-  message_loop_->PostTask(FROM_HERE, base::Bind(
-      &SerialWorker::OnWorkJobFinished, this));
+  task_runner_->PostTask(FROM_HERE,
+                         base::Bind(&SerialWorker::OnWorkJobFinished, this));
 }
 
 void SerialWorker::OnWorkJobFinished() {
-  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(task_runner_->BelongsToCurrentThread());
   switch (state_) {
     case CANCELLED:
       return;
     case WORKING:
       state_ = IDLE;
       this->OnWorkFinished();
       return;
     case PENDING:
       state_ = IDLE;
       WorkNow();
       return;
     default:
       NOTREACHED() << "Unexpected state " << state_;
   }
 }
 
 void SerialWorker::RetryWork() {
-  DCHECK(message_loop_->BelongsToCurrentThread());
+  DCHECK(task_runner_->BelongsToCurrentThread());
   switch (state_) {
     case CANCELLED:
       return;
     case WAITING:
       state_ = IDLE;
       WorkNow();
       return;
     default:
       NOTREACHED() << "Unexpected state " << state_;
   }
 }
 
 }  // namespace net