Add a policy to always show the Cast toolbar icon

chrome/app/chrome_command_ids.h

 // 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.
 
 #ifndef CHROME_APP_CHROME_COMMAND_IDS_H_
 #define CHROME_APP_CHROME_COMMAND_IDS_H_
 
 // This file lists all the command IDs understood by e.g. the browser.
 // It is used by Windows RC files, Mac NIB files, and other platforms too.
 
@@ skipping 317 matching lines @@
 #define IDC_STATUS_TRAY_KEEP_CHROME_RUNNING_IN_BACKGROUND 51100
 
 // Context menu items for media router
 #define IDC_MEDIA_ROUTER_ABOUT 51200
 #define IDC_MEDIA_ROUTER_HELP 51201
 #define IDC_MEDIA_ROUTER_LEARN_MORE 51202
 #define IDC_MEDIA_ROUTER_REPORT_ISSUE 51203
 #define IDC_MEDIA_ROUTER_ALWAYS_SHOW_TOOLBAR_ACTION 51204
 #define IDC_MEDIA_ROUTER_CLOUD_SERVICES_TOGGLE 51205
 #define IDC_MEDIA_ROUTER_MANAGE_DEVICES 51206
+#define IDC_MEDIA_ROUTER_SHOWN_BY_POLICY 51207
 
 // Context menu items for media stream status tray
 #define IDC_MEDIA_STREAM_DEVICE_STATUS_TRAY 51300
 #define IDC_MEDIA_CONTEXT_MEDIA_STREAM_CAPTURE_LIST_FIRST 51301
 #define IDC_MEDIA_CONTEXT_MEDIA_STREAM_CAPTURE_LIST_LAST 51399
 #define IDC_MEDIA_STREAM_DEVICE_ALWAYS_ALLOW 51400
 
 // Protocol handler menu entries
 #define IDC_CONTENT_CONTEXT_PROTOCOL_HANDLER_FIRST     52000
 #define IDC_CONTENT_CONTEXT_PROTOCOL_HANDLER_LAST      52199
 #define IDC_CONTENT_CONTEXT_PROTOCOL_HANDLER_SETTINGS  52200
 
 // Open link in profile entries
 #define IDC_OPEN_LINK_IN_PROFILE_FIRST 52300
 #define IDC_OPEN_LINK_IN_PROFILE_LAST  52399
 
 // NOTE: The last valid command value is 57343 (0xDFFF)
 // See http://msdn.microsoft.com/en-us/library/t2zechd4(VS.71).aspx
 
 // Starting command id for menus showing bookmarks (such as the wrench menu).
 // While command ids passed to Windows functions must not be higher than 0xDFFF,
 // these IDs are not exposed to the native system and thus can be in this
 // otherwise-reserved range. No command used in a menu (such as the wrench menu)
 // should be higher than this, otherwise it'll conflict.
 #define IDC_FIRST_BOOKMARK_MENU 0xE000
 
 #endif  // CHROME_APP_CHROME_COMMAND_IDS_H_