Use the task scheduler in the USB service on macOS and Windows

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;
-}
-
 namespace device {
 
 typedef struct libusb_device* PlatformUsbDevice;
 typedef struct libusb_context* PlatformUsbContext;
 
 class UsbDeviceImpl;
 
 class UsbServiceImpl :
 #if defined(OS_WIN)
     public DeviceMonitorWin::Observer,
 #endif  // OS_WIN
     public UsbService {
  public:
-  explicit UsbServiceImpl(
-      scoped_refptr<base::SequencedTaskRunner> blocking_task_runner);
+  UsbServiceImpl();
   ~UsbServiceImpl() override;
 
  private:
   // device::UsbService implementation
   void GetDevices(const GetDevicesCallback& callback) override;
 
 #if defined(OS_WIN)
   // device::DeviceMonitorWin::Observer implementation
   void OnDeviceAdded(const GUID& class_guid,
                      const std::string& device_path) override;
@@ skipping 61 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