Manage UsbService lifetime in DeviceClient implementations.

device/usb/usb_service_impl.cc

 // 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.
 
 #include "device/usb/usb_service_impl.h"
 
 #include <list>
 #include <set>
 
 #include "base/barrier_closure.h"
@@ skipping 544 matching lines @@
   RefreshDevices();
 #if defined(OS_WIN)
   DeviceMonitorWin* device_monitor = DeviceMonitorWin::GetForAllInterfaces();
   if (device_monitor) {
     device_observer_.Add(device_monitor);
   }
 #endif  // OS_WIN
 }
 
 UsbServiceImpl::~UsbServiceImpl() {
-
   if (hotplug_enabled_) {
     libusb_hotplug_deregister_callback(context_->context(), hotplug_handle_);
   }
   for (const auto& map_entry : devices_) {
     map_entry.second->OnDisconnect();
   }
 }
 
 scoped_refptr<UsbDevice> UsbServiceImpl::GetDevice(const std::string& guid) {
   DCHECK(CalledOnValidThread());
@@ skipping 278 matching lines @@
   PlatformDeviceMap::iterator it = platform_devices_.find(platform_device);
   if (it != platform_devices_.end()) {
     RemoveDevice(it->second);
   } else {
     devices_being_enumerated_.erase(platform_device);
   }
   libusb_unref_device(platform_device);
 }
 
 }  // namespace device