Add experiment for having a "Beta forum" link in the help menu.

chrome/browser/ui/toolbar/app_menu_model.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_BROWSER_UI_TOOLBAR_APP_MENU_MODEL_H_
 #define CHROME_BROWSER_UI_TOOLBAR_APP_MENU_MODEL_H_
 
 #include <memory>
 
 #include "base/files/file_path.h"
@@ skipping 53 matching lines @@
   MENU_ACTION_OPTIONS = 36,
   MENU_ACTION_ABOUT = 37,
   MENU_ACTION_HELP_PAGE_VIA_MENU = 38,
   MENU_ACTION_FEEDBACK = 39,
   MENU_ACTION_TOGGLE_REQUEST_TABLET_SITE = 40,
   MENU_ACTION_EXIT = 43,
   MENU_ACTION_RECENT_TAB = 41,
   MENU_ACTION_BOOKMARK_OPEN = 42,
   MENU_ACTION_UPGRADE_DIALOG = 44,
   MENU_ACTION_CAST = 45,
+  MENU_ACTION_BETA_FORUM = 46,
   LIMIT_MENU_ACTION
 };
 
 // A menu model that builds the contents of the zoom menu.
 class ZoomMenuModel : public ui::SimpleMenuModel {
  public:
   explicit ZoomMenuModel(ui::SimpleMenuModel::Delegate* delegate);
   ~ZoomMenuModel() override;
 
  private:
@@ skipping 138 matching lines @@
   Browser* browser_;  // weak
 
   std::unique_ptr<content::HostZoomMap::Subscription>
       browser_zoom_subscription_;
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(AppMenuModel);
 };
 
 #endif  // CHROME_BROWSER_UI_TOOLBAR_APP_MENU_MODEL_H_