Add a skeleton Start Page to the experimental app list.

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 {
 
-APP_LIST_EXPORT extern const char kEnableExperimentalAppList[];
+// Please keep this list sorted.
 APP_LIST_EXPORT extern const char kDisableFolderUI[];
 APP_LIST_EXPORT extern const char kDisableVoiceSearch[];
+APP_LIST_EXPORT extern const char kEnableAppInfo[];
+APP_LIST_EXPORT extern const char kEnableExperimentalAppList[];
 APP_LIST_EXPORT extern const char kEnableHotwordAlwaysOn[];
-APP_LIST_EXPORT extern const char kEnableAppInfo[];
+APP_LIST_EXPORT extern const char kShowAppListStartPage[];
 
 bool APP_LIST_EXPORT IsFolderUIEnabled();
 
 bool APP_LIST_EXPORT IsVoiceSearchEnabled();
 
 bool APP_LIST_EXPORT IsHotwordAlwaysOnEnabled();
 
 bool APP_LIST_EXPORT IsAppInfoEnabled();
 
 bool APP_LIST_EXPORT IsExperimentalAppListEnabled();
 
+bool APP_LIST_EXPORT IsStartPageWebUIEnabled();
+
 }  // namespace switches
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_APP_LIST_SWITCHES_H_