Revert of Remove disable-app-list-voice-search flag.

ui/app_list/app_list_switches.h

 // Copyright 2013 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.
 
 #ifndef UI_APP_LIST_APP_LIST_SWITCHES_H_
 #define UI_APP_LIST_APP_LIST_SWITCHES_H_
 
 #include "ui/app_list/app_list_export.h"
 
 namespace app_list {
 namespace switches {
 
 // Please keep these flags sorted.
 APP_LIST_EXPORT extern const char kDisableAppInfo[];
 APP_LIST_EXPORT extern const char kDisableSyncAppList[];
+APP_LIST_EXPORT extern const char kDisableVoiceSearch[];
 APP_LIST_EXPORT extern const char kEnableCenteredAppList[];
 APP_LIST_EXPORT extern const char kEnableDriveAppsInAppList[];
 APP_LIST_EXPORT extern const char kEnableExperimentalAppList[];
 APP_LIST_EXPORT extern const char kEnableHotwordAlwaysOn[];
 APP_LIST_EXPORT extern const char kEnableSyncAppList[];
 
 bool APP_LIST_EXPORT IsAppListSyncEnabled();
 
 bool APP_LIST_EXPORT IsFolderUIEnabled();
 
 bool APP_LIST_EXPORT IsVoiceSearchEnabled();
 
 bool APP_LIST_EXPORT IsAppInfoEnabled();
 
 bool APP_LIST_EXPORT IsExperimentalAppListEnabled();
 
 // Determines whether either command-line switch was given for enabling the
 // centered app list position. Do not use this when positioning the app list;
 // instead use AppListViewDelegate::ShouldCenterWindow. It checks a superset of
 // the conditions that trigger the position.
 bool APP_LIST_EXPORT IsCenteredAppListEnabled();
 
 bool APP_LIST_EXPORT IsDriveAppsInAppListEnabled();
 
 }  // namespace switches
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_APP_LIST_SWITCHES_H_