Add a UsbService::Observer function for cleanup actions.

device/usb/usb_service.cc

 // 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 "base/message_loop/message_loop.h"
 #include "device/usb/usb_device.h"
 #include "device/usb/usb_service_impl.h"
 
@@ skipping 26 matching lines @@
 
   UsbService* usb_service_;
 };
 
 void UsbService::Observer::OnDeviceAdded(scoped_refptr<UsbDevice> device) {
 }
 
 void UsbService::Observer::OnDeviceRemoved(scoped_refptr<UsbDevice> device) {
 }
 
+void UsbService::Observer::OnDeviceRemovedCleanup(
+    scoped_refptr<UsbDevice> device) {
+}
+
 // static
 UsbService* UsbService::GetInstance(
     scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner) {
   if (!g_service) {
     g_service = UsbServiceImpl::Create(ui_task_runner);
     // This object will clean itself up when the message loop is destroyed.
     new Destroyer(g_service);
   }
   return g_service;
 }
@@ skipping 21 matching lines @@
 }
 
 void UsbService::NotifyDeviceAdded(scoped_refptr<UsbDevice> device) {
   DCHECK(CalledOnValidThread());
   FOR_EACH_OBSERVER(Observer, observer_list_, OnDeviceAdded(device));
 }
 
 void UsbService::NotifyDeviceRemoved(scoped_refptr<UsbDevice> device) {
   DCHECK(CalledOnValidThread());
   FOR_EACH_OBSERVER(Observer, observer_list_, OnDeviceRemoved(device));
+  FOR_EACH_OBSERVER(Observer, observer_list_, OnDeviceRemovedCleanup(device));
 }
 
 }  // namespace device