Move the serial API to extensions/.

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 23 matching lines @@
       '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',
         ],
-      }]
+      }],
+      ['chromeos==1', {
+        'dependencies': [
+          '../chromeos/chromeos.gyp:chromeos',
+        ],
+      }],
     ]
   }],
 }