Remove hotword installation code at compile time if hotwording disabled.

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 35 matching lines @@
   # --debug-devtools cmdline switch.
   debug_devtools = false
 
   # Enables WebRTC.
   # TODO(GYP) make mac and android work.
   enable_webrtc = !is_ios && !is_mac && !is_android
 
   # Enables the Media Router.
   enable_media_router = !is_ios && !is_android
 
+  # 'Ok Google' hotwording is disabled by default in open source builds. Set to
+  # true to enable. (This will download a closed-source NaCl module at startup.)
+  # Chrome-branded builds have this enabled by default.
+  enable_hotwording = is_chrome_branded
+
   # Enables proprietary codecs and demuxers; e.g. H264, MOV, AAC, and MP3.
   # Android OS includes support for proprietary codecs regardless of building
   # Chromium or Google Chrome. We also ship Google Chrome and Chromecast with
   # proprietary codecs.
   # TODO(GYP) The GYP build has || chromecast==1 for this:
   proprietary_codecs = is_android || is_chrome_branded
 
   enable_configuration_policy = true
 
   # Enables support for background apps.
@@ skipping 124 matching lines @@
 # 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)