Only enable Hotwords when extensions are enabled.

chrome/chrome_browser_ui.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': {
     'chrome_browser_ui_non_ios_sources': [
       'browser/ui/accelerator_utils.h',
       'browser/ui/android/android_about_app_info.cc',
       'browser/ui/android/android_about_app_info.h',
@@ skipping 1115 matching lines @@
       'browser/ui/webui/user_actions/user_actions_ui.cc',
       'browser/ui/webui/user_actions/user_actions_ui.h',
       'browser/ui/webui/user_actions/user_actions_ui_handler.cc',
       'browser/ui/webui/user_actions/user_actions_ui_handler.h',
       'browser/ui/webui/version_handler.cc',
       'browser/ui/webui/version_handler_chromeos.cc',
       'browser/ui/webui/version_handler_chromeos.h',
       'browser/ui/webui/version_handler.h',
       'browser/ui/webui/version_ui.cc',
       'browser/ui/webui/version_ui.h',
-      'browser/ui/webui/voicesearch_ui.cc',
-      'browser/ui/webui/voicesearch_ui.h',
       'browser/ui/webui/welcome_handler_android.cc',
       'browser/ui/webui/welcome_handler_android.h',
       'browser/ui/webui/welcome_ui_android.cc',
       'browser/ui/webui/welcome_ui_android.h',
       'browser/ui/window_sizer/window_sizer_mac.mm',
       'browser/ui/zoom/zoom_controller.cc',
       'browser/ui/zoom/zoom_controller.h',
       'browser/ui/zoom/zoom_event_manager.cc',
       'browser/ui/zoom/zoom_event_manager.h',
       'browser/ui/zoom/zoom_observer.h',
@@ skipping 1371 matching lines @@
       'browser/ui/views/javascript_app_modal_event_blocker_x11.cc',
       'browser/ui/views/javascript_app_modal_event_blocker_x11.h',
       'browser/ui/views/tabs/window_finder_x11.cc',
     ],
     # Files used on iOS. iOS uses only these files and does not share other
     # lists, so a file may appear here and in the non_ios_sources also.
     'chrome_browser_ui_ios_sources': [
       'browser/ui/profile_error_dialog.cc',
       'browser/ui/profile_error_dialog.h',
     ],
+    'chrome_browser_ui_extensions_sources': [
+      'browser/ui/webui/voicesearch_ui.cc',
+      'browser/ui/webui/voicesearch_ui.h',
+    ],
   },
   'targets': [
     {
       'target_name': 'browser_ui',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
       # Since browser and browser_ui actually depend on each other,
       # we must omit the dependency from browser_ui to browser.
       # However, this means browser_ui and browser should more or less
       # have the same dependencies. Once browser_ui is untangled from
@@ skipping 382 matching lines @@
               'sources': [
                 '<@(chrome_browser_ui_autofill_dialog_non_mobile_sources)',
               ],
               'dependencies': [
                 '../third_party/libaddressinput/libaddressinput.gyp:libaddressinput',
                 '../third_party/libaddressinput/libaddressinput.gyp:libaddressinput_strings',
               ],
             }],
           ],
         }],
+        ['enable_extensions==1', {
+          'sources': [ '<@(chrome_browser_ui_extensions_sources)' ],
+        }],
         ['enable_google_now==1 and OS!="android"', {
           'sources': [ '<@(chrome_browser_ui_google_now_non_android_sources)' ],
         }],
         ['enable_webrtc==1', {
           'sources': [ '<@(chrome_browser_ui_webrtc_sources)' ],
         }],
         ['enable_service_discovery==1', {
           'sources': [ '<@(chrome_browser_ui_service_discovery_sources)' ],
         }],
         ['enable_spellcheck==1', {
           'dependencies': [
             '../third_party/hunspell/hunspell.gyp:hunspell',
           ],
         }],
       ],
     },
   ],
 }