[WebMIDI] Introduce UsbMidi{Input, Output}Stream.

media/midi/usb_midi_device.h

Index: media/midi/usb_midi_device.h
diff --git a/media/midi/usb_midi_device.h b/media/midi/usb_midi_device.h
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index 0000000000000000000000000000000000000000..77bbd54fbce9d38047aeaf9d42838e799e0a2059
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+++ b/media/midi/usb_midi_device.h
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+// Copyright (c) 2013 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_USB_MIDI_DEVICE_H_
+#define MEDIA_MIDI_USB_MIDI_DEVICE_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/memory/scoped_vector.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class MEDIA_EXPORT UsbMidiDeviceDelegate {
+ public:
+  virtual ~UsbMidiDeviceDelegate() {}
+  virtual void ReceiveUsbMidiData(int endpoint_number,
+                                  const uint8* data,
+                                  size_t size,
+                                  double timestamp) = 0;
+};
+
+class MEDIA_EXPORT UsbMidiDevice {
+ public:
+  typedef ScopedVector<UsbMidiDevice> Devices;
+  class Factory {
+   public:
+    typedef base::Callback<void(bool result, Devices* devices)> Callback;
+    virtual ~Factory() {}
+    // Enumerates devices.
+    // Devices that have no USB-MIDI interfaces can be omitted.
+    // When the operation succeeds, |callback| will be called with |true| and
+    // devices.
+    // Otherwise |callback| will be called with |false| and empty devices.
+    // When this factory is destroyed during the operation, the operation
+    // will be canceled silently (i.e. |callback| will not be called).
+    virtual void EnumerateDevices(Callback callback) = 0;
+  };
+
+  virtual ~UsbMidiDevice() {}
+
+  // Returns the descriptor of this device.
+  virtual std::vector<uint8> GetDescriptor() = 0;
+
+  // Sends |data| to the given USB endpoint of this device.
+  virtual void Send(int endpoint_number, const std::vector<uint8>& data) = 0;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MIDI_USB_MIDI_DEVICE_H_