media: Cleanup class/struct forward declarations

media/midi/usb_midi_device.h

 // Copyright 2014 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 <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/memory/scoped_vector.h"
 #include "base/time/time.h"
 #include "media/midi/usb_midi_export.h"
 
 namespace midi {
 
-class MidiManagerUsb;
 class UsbMidiDevice;
 
 // Delegate class for UsbMidiDevice.
 // Each method is called when an corresponding event arrives at the device.
 class USB_MIDI_EXPORT UsbMidiDeviceDelegate {
  public:
   virtual ~UsbMidiDeviceDelegate() {}
 
   // Called when USB-MIDI data arrives at |device|.
   virtual void ReceiveUsbMidiData(UsbMidiDevice* device,
@@ skipping 49 matching lines @@
   // Return the device version.
   virtual std::string GetDeviceVersion() = 0;
 
   // Sends |data| to the given USB endpoint of this device.
   virtual void Send(int endpoint_number, const std::vector<uint8_t>& data) = 0;
 };
 
 }  // namespace midi
 
 #endif  // MEDIA_MIDI_USB_MIDI_DEVICE_H_