device: Cleanup class/struct forward declarations

device/usb/usb_device_handle_impl.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 DEVICE_USB_USB_DEVICE_HANDLE_IMPL_H_
 #define DEVICE_USB_USB_DEVICE_HANDLE_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 20 matching lines @@
 }
 
 namespace device {
 
 struct EndpointMapValue {
   const UsbInterfaceDescriptor* interface;
   const UsbEndpointDescriptor* endpoint;
 };
 
 class UsbContext;
-struct UsbConfigDescriptor;
 class UsbDeviceImpl;
 
 typedef libusb_device_handle* PlatformUsbDeviceHandle;
 typedef libusb_iso_packet_descriptor* PlatformUsbIsoPacketDescriptor;
 typedef libusb_transfer* PlatformUsbTransferHandle;
 
 // UsbDeviceHandle class provides basic I/O related functionalities.
 class UsbDeviceHandleImpl : public UsbDeviceHandle {
  public:
   scoped_refptr<UsbDevice> GetDevice() const override;
@@ skipping 156 matching lines @@
   scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbDeviceHandleImpl);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_USB_USB_DEVICE_HANDLE_IMPL_H_