MidiScheduler binds to task runner of constructing thread

media/midi/midi_scheduler.cc

Index: media/midi/midi_scheduler.cc
diff --git a/media/midi/midi_scheduler.cc b/media/midi/midi_scheduler.cc
index 4f6f68c2578c4373d4e1b9c2a6d312519d619d32..810b257d96d1880e66c61b5ab3747c7c66aeb082 100644
--- a/media/midi/midi_scheduler.cc
+++ b/media/midi/midi_scheduler.cc
@@ -8,7 +8,6 @@
 
 #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"
@@ -17,15 +16,17 @@ 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,
@@ -46,13 +47,13 @@ void MidiScheduler::PostSendDataTask(MidiManagerClient* client,
                                 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);
 }