Add stubs for brailleDisplayPrivate extension API.

chrome/common/extensions/api/api.gyp

 # 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.
 
 {
   'targets': [
     {
       'target_name': 'api',
       'type': 'static_library',
       'sources': [
@@ skipping 12 matching lines @@
           'activity_log_private.json',
           'adview.json',
           'app_current_window_internal.idl',
           'app_runtime.idl',
           'app_window.idl',
           'audio.idl',
           'autotest_private.idl',
           'bluetooth.idl',
           'bookmark_manager_private.json',
           'bookmarks.json',
+          'braille_display_private.idl',
           'browsing_data.json',
           'chromeos_info_private.json',
           'cloud_print_private.json',
           'command_line_private.json',
           'content_settings.json',
           'context_menus.json',
           'cookies.json',
           'debugger.json',
           'developer_private.idl',
           'desktop_capture.idl',
@@ skipping 121 matching lines @@
           'schema_files!': [
             'file_browser_handler_internal.json',
             'log_private.idl',
             'rtc_private.idl',
           ],
         }],
       ],
     },
   ],
 }