Split bundle generation steps so that API registration is generated in browser, not common.

device/serial/serial.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 67 matching lines @@
         'serial_device_enumerator_win.h',
         'serial_io_handler.cc',
         'serial_io_handler.h',
         'serial_io_handler_posix.cc',
         'serial_io_handler_posix.h',
         'serial_io_handler_win.cc',
         'serial_io_handler_win.h',
         'serial_service_impl.cc',
         'serial_service_impl.h',
       ],
+      'hard_dependency': 1,  # Generates included header files.
     },
     {
       # GN version: //device/serial:test_util
       'target_name': 'device_serial_test_util',
       'type': 'static_library',
       'dependencies': [
         'device_serial',
         'device_serial_mojo',
       ],
       'sources': [
         'test_serial_io_handler.cc',
         'test_serial_io_handler.h',
       ],
     },
   ],
 }