Add components and CLD to GN build.

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': [{
+    # GN version: //components/usb_service
     'target_name': 'usb_service',
     'type': '<(component)',
     'dependencies': [
       '../base/base.gyp:base',
       '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
       '../content/content.gyp:content_browser',
       '../net/net.gyp:net',
       '../third_party/libusb/libusb.gyp:libusb',
     ],
     'defines': [
       'USB_SERVICE_IMPLEMENTATION',
     ],
     'include_dirs': [
       '..',
     ],
     'sources': [
+      # Note: sources list duplicated in GN build.
       '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',
         ],
       }]
     ]
   }],
 }