[WebMIDI] Introduce MidiManagerUsb

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
index 3f29d64f985c626fe7b195df71a609de0b35a8bb..59f129d1ffaa93bd4fa31f50bf70e4c4284f0630 100644
--- a/media/midi/usb_midi_device.h
+++ b/media/midi/usb_midi_device.h
@@ -8,15 +8,53 @@
 #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 UsbMidiDevice;
+
+// Delegate class for UsbMidiDevice.
+// Each method is called when an corresponding event arrives at the device.
+class MEDIA_EXPORT UsbMidiDeviceDelegate {
+ public:
+  virtual ~UsbMidiDeviceDelegate() {}
+
+  // Called when USB-MIDI data arrives at |device|.
+  virtual void ReceiveUsbMidiData(UsbMidiDevice* device,
+                                  int endpoint_number,
+                                  const uint8* data,
+                                  size_t size,
+                                  double timestamp) = 0;
+};
+
 // UsbMidiDevice represents a USB-MIDI device.
 // This is an interface class and each platform-dependent implementation class
 // will be a derived class.
 class MEDIA_EXPORT UsbMidiDevice {
  public:
+  typedef ScopedVector<UsbMidiDevice> Devices;
+
+  // Factory class for USB-MIDI devices.
+  // Each concrete implementation will find and create devices
+  // in platform-dependent way.
+  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(UsbMidiDeviceDelegate* delegate,
+                                  Callback callback) = 0;
+  };
+
   virtual ~UsbMidiDevice() {}
 
   // Returns the descriptor of this device.