device: Cleanup class/struct forward declarations

device/usb/usb_service_linux.h

 // Copyright 2016 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 <list>
 #include <memory>
 #include <unordered_map>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "device/usb/usb_service.h"
 
 namespace base {
 class SequencedTaskRunner;
-class SingleThreadTaskRunner;
 }
 
 namespace device {
 
 struct UsbDeviceDescriptor;
 class UsbDeviceLinux;
 
 class UsbServiceLinux : public UsbService {
  public:
   explicit UsbServiceLinux(
@@ skipping 35 matching lines @@
 
   std::unique_ptr<FileThreadHelper> helper_;
   DeviceMap devices_by_path_;
 
   base::WeakPtrFactory<UsbServiceLinux> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbServiceLinux);
 };
 
 }  // namespace device