Fix missing callback chaining in UsbService.

chrome/browser/usb/usb_service.cc

 // Copyright (c) 2012 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 "chrome/browser/usb/usb_service.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 52 matching lines @@
 
 UsbService::~UsbService() {}
 
 void UsbService::Cleanup() {
   event_handler_->Stop();
   event_handler_ = NULL;
 }
 
 void UsbService::FindDevices(const uint16 vendor_id,
                              const uint16 product_id,
-                             vector<scoped_refptr<UsbDevice> >* devices) {
+                             vector<scoped_refptr<UsbDevice> >* devices,
+                             const base::Callback<void()>& callback) {
   DCHECK(event_handler_) << "FindDevices called after event handler stopped.";
 #if defined(OS_CHROMEOS)
   chromeos::PermissionBrokerClient* client =
       chromeos::DBusThreadManager::Get()->GetPermissionBrokerClient();
   DCHECK(client) << "Could not get permission broker client.";
-  if (!client)
+  if (!client) {
+    callback.Run();
     return;
+  }
+
   client->RequestUsbAccess(vendor_id,
                            product_id,
                            base::Bind(&UsbService::FindDevicesImpl,
                                       base::Unretained(this),
                                       vendor_id,
                                       product_id,
-                                      devices));
+                                      devices,
+                                      callback));
 #else
-  FindDevicesImpl(vendor_id, product_id, devices, true);
+  FindDevicesImpl(vendor_id, product_id, devices, callback, true);
 #endif  // defined(OS_CHROMEOS)
 }
 
 void UsbService::FindDevicesImpl(const uint16 vendor_id,
                                  const uint16 product_id,
                                  vector<scoped_refptr<UsbDevice> >* devices,
+                                 const base::Callback<void()>& callback,
                                  bool success) {
+  base::ScopedClosureRunner run_callback(callback);
+
   devices->clear();
 
   // If the permission broker was unable to obtain permission for the specified
   // devices then there is no point in attempting to enumerate the devices. On
   // platforms without a permission broker, we assume permission is granted.
   if (!success)
     return;
 
   DeviceVector enumerated_devices;
   EnumerateDevices(&enumerated_devices);
@@ skipping 73 matching lines @@
     if (libusb_open(device, &handle)) {
       LOG(WARNING) << "Could not open device.";
       return NULL;
     }
 
     UsbDevice* wrapper = new UsbDevice(this, handle);
     devices_[device] = wrapper;
   }
   return devices_[device];
 }