Add build flag to disable hotwording.

build/common.gypi

 # 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 373 matching lines @@
       # 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.
       'safe_browsing%': 1,
 
       # Web speech is enabled by default. Set to 0 to disable.
       'enable_web_speech%': 1,
 
+      # 'Ok Google' hotwording is enabled by default. Set to 0 to disable.
+      'enable_hotwording%': 1,
+
       # Notifications are compiled in by default. Set to 0 to disable.
       'notifications%' : 1,
 
       # Use dsymutil to generate real .dSYM files on Mac. The default is 0 for
       # regular builds and 1 for ASan builds.
       'mac_want_real_dsym%': 'default',
 
       # If this is set, the clang plugins used on the buildbot will be used.
       # Run tools/clang/scripts/update.sh to make sure they are compiled.
       # This causes 'clang_chrome_plugins_flags' to be set.
@@ skipping 725 matching lines @@
     'use_third_party_translations%': '<(use_third_party_translations)',
     'remoting%': '<(remoting)',
     'enable_one_click_signin%': '<(enable_one_click_signin)',
     'enable_pre_sync_backup%': '<(enable_pre_sync_backup)',
     'enable_media_router%': '<(enable_media_router)',
     'enable_webrtc%': '<(enable_webrtc)',
     'chromium_win_pch%': '<(chromium_win_pch)',
     'configuration_policy%': '<(configuration_policy)',
     'safe_browsing%': '<(safe_browsing)',
     'enable_web_speech%': '<(enable_web_speech)',
+    'enable_hotwording%': '<(enable_hotwording)',
     'notifications%': '<(notifications)',
     'clang_use_chrome_plugins%': '<(clang_use_chrome_plugins)',
     'mac_want_real_dsym%': '<(mac_want_real_dsym)',
     'asan%': '<(asan)',
     'asan_blacklist%': '<(asan_blacklist)',
     'asan_coverage%': '<(asan_coverage)',
     'sanitizer_coverage%': '<(sanitizer_coverage)',
     'asan_field_padding%': '<(asan_field_padding)',
     'use_sanitizer_options%': '<(use_sanitizer_options)',
     'syzyasan%': '<(syzyasan)',
@@ skipping 5046 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }