Log errors from libusb.

components/usb_service.gypi

 # 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.
 
 {
   'targets': [{
     'target_name': 'usb_service',
     'type': '<(component)',
     'dependencies': [
       '../base/base.gyp:base',
@@ skipping 10 matching lines @@
     ],
     'sources': [
       'usb_service/usb_context.cc',
       'usb_service/usb_context.h',
       'usb_service/usb_device_impl.cc',
       'usb_service/usb_device_impl.h',
       'usb_service/usb_device.h',
       'usb_service/usb_device_handle_impl.cc',
       'usb_service/usb_device_handle_impl.h',
       'usb_service/usb_device_handle.h',
+      'usb_service/usb_error.cc',
+      'usb_service/usb_error.h',
       'usb_service/usb_interface.h',
       'usb_service/usb_interface_impl.cc',
       'usb_service/usb_interface_impl.h',
       'usb_service/usb_service.h',
       'usb_service/usb_service_impl.cc',
     ],
     'conditions': [
       ['OS == "linux"', {
         'dependencies': [
           '../build/linux/system.gyp:udev',
         ],
       }]
     ]
   }],
 }