Web MIDI: introduce MidiService class

media/midi/midi_service.h

+// Copyright 2016 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.
+
+#ifndef MEDIA_MIDI_MIDI_SERVICE_H_
+#define MEDIA_MIDI_MIDI_SERVICE_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/synchronization/lock.h"
+#include "media/midi/midi_export.h"
+#include "media/midi/midi_manager.h"
+
+namespace midi {
+
+// 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.
+class MIDI_EXPORT MidiService final {
+ public:
+  // |MidiManager| can be explicitly specified in the constructor for testing.
+  explicit MidiService(std::unique_ptr<MidiManager> manager = nullptr);
+  ~MidiService();
+
+  // Called on the browser main thread to notify the I/O thread will stop and
+  // the instance will be destructed on the main thread soon.
+  void Shutdown();
+
+  // A client calls StartSession() to receive and send MIDI data.
+  void StartSession(MidiManagerClient* client);
+
+  // A client calls EndSession() to stop receiving MIDI data.
+  void EndSession(MidiManagerClient* client);
+
+  // A client calls DispatchSendMidiData() to send MIDI data.
+  virtual void DispatchSendMidiData(MidiManagerClient* client,
+                                    uint32_t port_index,
+                                    const std::vector<uint8_t>& data,
+                                    double timestamp);
+
+  std::unique_ptr<MidiManager> manager_;
+  base::Lock lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(MidiService);
+};
+
+}  // namespace midi
+
+#endif  // MEDIA_MIDI_MIDI_SERVICE_H_