Web MIDI: implement TaskService

media/midi/midi_service.h

Index: media/midi/midi_service.h
diff --git a/media/midi/midi_service.h b/media/midi/midi_service.h
index 3017b862239c6b61081ca0b1e872ebb44b10a86e..fb84e0a668a70dabfb628ac968bff743cd594c8e 100644
--- a/media/midi/midi_service.h
+++ b/media/midi/midi_service.h
@@ -20,6 +20,8 @@
 
 namespace midi {
 
+class TaskService;
+
 // Manages MidiManager backends.  This class expects to be constructed and
 // destructed on the browser main thread, but methods can be called on both
 // the main thread and the I/O thread.
@@ -54,14 +56,21 @@ class MIDI_EXPORT MidiService final {
   // MidiManager, each task should ensure that MidiManager that posted the task
   // is still alive while accessing |this|. TaskRunners will be reused when
   // another MidiManager is instantiated.
+  // TODO(toyoshim): Remove this interface.
   scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner(size_t runner_id);
 
+  // Obtains a TaskService that lives with MidiService.
+  TaskService* task_service() { return task_service_.get(); }
+
  private:
   // Holds MidiManager instance. If the dynamic instantiation feature is
   // enabled, the MidiManager would be constructed and destructed on the I/O
   // thread, and all MidiManager methods would be called on the I/O thread.
   std::unique_ptr<MidiManager> manager_;
 
+  // Holds TaskService instance.
+  std::unique_ptr<TaskService> task_service_;
+
   // TaskRunner to destruct |manager_| on the right thread.
   scoped_refptr<base::SingleThreadTaskRunner> manager_destructor_runner_;