Add build flag to disable hotwording.

chrome/chrome_browser.gypi

 # Copyright 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.
 
 {
   'variables': {
     # All .cc, .h, .m, and .mm files under browser except for:
     # * tests and mocks.
     # * code below browser/chromeos
     # * code below browser/extensions
@@ skipping 3555 matching lines @@
         # Partial-only printing support.
         ['enable_basic_printing==1 and enable_print_preview==0', {
           'sources': [ '<@(chrome_browser_printing_basic_only_sources)' ],
         }],
         ['enable_captive_portal_detection==1', {
           'sources': [ '<@(chrome_browser_captive_portal_sources)' ]
         }],
         ['enable_session_service==1', {
           'sources': [ '<@(chrome_browser_session_service_sources)' ],
         }],
+        ['enable_hotwording==1', {
+          'defines': [ 'ENABLE_HOTWORDING' ],
+        }],
         ['OS!="android" and OS!="ios" and chromeos==0', {
           'sources': [ '<@(chrome_browser_desktop_sources)' ],
         }],
         ['OS=="android" or OS=="ios"', {
           'sources': [ '<@(chrome_browser_mobile_sources)' ],
         }, {  # OS!="android" and OS!="ios"
           'sources': [ '<@(chrome_browser_non_mobile_sources)' ],
           'dependencies': [
             '../components/components.gyp:feedback_component',
             '../device/core/core.gyp:device_core',
@@ skipping 409 matching lines @@
           'variables': {
             'proto_in_dir': 'browser/sync_file_system/drive_backend',
             'proto_out_dir': 'chrome/browser/sync_file_system/drive_backend',
           },
           'includes': [ '../build/protoc.gypi' ]
         },
       ],
     },],
   ],
 }