device: Cleanup class/struct forward declarations

device/usb/usb_service_impl.h

 // Copyright 2015 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.
 
 #include "device/usb/usb_service.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <queue>
 #include <set>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "build/build_config.h"
 #include "device/usb/usb_context.h"
 #include "device/usb/usb_device_impl.h"
 #include "third_party/libusb/src/libusb/libusb.h"
 
 #if defined(OS_WIN)
 #include "base/scoped_observer.h"
 #include "device/base/device_monitor_win.h"
 #endif  // OS_WIN
 
 struct libusb_device;
 struct libusb_context;
 
 namespace base {
 class SequencedTaskRunner;
-class SingleThreadTaskRunner;
 }
 
 namespace device {
 
 typedef struct libusb_device* PlatformUsbDevice;
 typedef struct libusb_context* PlatformUsbContext;
 
 class UsbServiceImpl :
 #if defined(OS_WIN)
     public DeviceMonitorWin::Observer,
@@ skipping 73 matching lines @@
 #if defined(OS_WIN)
   ScopedObserver<DeviceMonitorWin, DeviceMonitorWin::Observer> device_observer_;
 #endif  // OS_WIN
 
   base::WeakPtrFactory<UsbServiceImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbServiceImpl);
 };
 
 }  // namespace device