Allow enable_hangout_services_extension overriding in gn build

build/config/features.gni

 # 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.
 
 # This file contains Chrome-feature-related build flags (see ui.gni for
 # UI-related ones). These should theoretically be moved to the build files of
 # the features themselves.
 #
 # However, today we have many "bad" dependencies on some of these flags from,
 # e.g. base, so they need to be global to match the GYP configuration. Also,
@@ skipping 75 matching lines @@
 
   enable_remoting = !is_ios && !is_android
 
   # Enable hole punching for the protected video.
   enable_video_hole = is_android
 
   # Enables browser side Content Decryption Modules. Required for embedders
   # (e.g. Android and ChromeCast) that use a browser side CDM.
   enable_browser_cdms = is_android
 
+  # Hangout services is an extension that adds extra features to Hangouts.
+  # For official GYP builds, this flag is set.
+  enable_hangout_services_extension = false
+
   # Enables the use of CDMs in pepper plugins. Chromecast requires that this
   # can be explicitly disabled in gn args.
   enable_pepper_cdms = enable_plugins && (is_linux || is_mac || is_win)
 
   # Variable safe_browsing is used to control the build time configuration
   # for safe browsing feature. Safe browsing can be compiled in 4 different
   # levels: 0 disables it, 1 enables it fully, and 2 enables only UI and
   # reporting features for use with Data Saver on Mobile, and 3 enables
   # extended mobile protection via an external API.  When 3 is fully deployed,
   # it will replace 2.
@@ skipping 87 matching lines @@
 enable_chromevox_next = false
 
 # Use brlapi from brltty for braille display support.
 use_brlapi = is_chromeos
 
 # Option controlling the use of GConf (the classic GNOME configuration
 # system).
 # TODO(GYP) also require !embedded to enable.
 use_gconf = is_linux && !is_chromeos
 
-# Hangout services is an extension that adds extra features to Hangouts.
-# For official GYP builds, this flag is set, it will likely need to be
-# parameterized in the future for a similar use.
-enable_hangout_services_extension = false
-
 # Whether to back up data before sync.
 enable_pre_sync_backup = is_win || is_mac || (is_linux && !is_chromeos)
 
 # WebVR support disabled until platform implementations have been added
 enable_webvr = false