MidiScheduler binds to task runner of constructing thread

media/midi/midi_scheduler.cc

 // Copyright 2015 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 "media/midi/midi_scheduler.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/location.h"
-#include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "media/midi/midi_manager.h"
 
 namespace media {
 namespace midi {
 
 MidiScheduler::MidiScheduler(MidiManager* manager)
-  : manager_(manager),
-    weak_factory_(this) {
-}
+    : manager_(manager),
+      task_runner_(base::ThreadTaskRunnerHandle::Get()),
+      weak_factory_(this) {}
 
 MidiScheduler::~MidiScheduler() {
+  DCHECK(thread_checker_.CalledOnValidThread());
 }
 
 // TODO(crbug.com/467442): Use CancelableTaskTracker once it supports
 // DelayedTask.
+// TODO(shaochuan): Unit tests to ensure thread safety.
 void MidiScheduler::PostSendDataTask(MidiManagerClient* client,
                                      size_t length,
                                      double timestamp,
                                      const base::Closure& closure) {
   DCHECK(client);
 
   const base::Closure& weak_closure = base::Bind(
       &MidiScheduler::InvokeClosure,
       weak_factory_.GetWeakPtr(),
       client,
       length,
       closure);
 
   base::TimeDelta delay;
   if (timestamp != 0.0) {
     base::TimeTicks time_to_send =
         base::TimeTicks() + base::TimeDelta::FromMicroseconds(
                                 timestamp * base::Time::kMicrosecondsPerSecond);
     delay = std::max(time_to_send - base::TimeTicks::Now(), base::TimeDelta());
   }
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(FROM_HERE, weak_closure,
-                                                       delay);
+  task_runner_->PostDelayedTask(FROM_HERE, weak_closure, delay);
 }
 
 void MidiScheduler::InvokeClosure(MidiManagerClient* client,
                                   size_t length,
                                   const base::Closure& closure) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   closure.Run();
   manager_->AccumulateMidiBytesSent(client, length);
 }
 
 }  // namespace midi
 }  // namespace media