Remove old (dead) app list code.

ui/app_list/views/start_page_view.h

 // Copyright 2014 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_VIEWS_START_PAGE_VIEW_H_
 #define UI_APP_LIST_VIEWS_START_PAGE_VIEW_H_
 
 #include <stddef.h>
 
 #include <vector>
 
 #include "base/macros.h"
 #include "ui/app_list/app_list_export.h"
 #include "ui/app_list/views/app_list_page.h"
 
 namespace app_list {
 
 class AllAppsTileItemView;
 class AppListMainView;
 class AppListViewDelegate;
 class CustomLauncherPageBackgroundView;
 class SearchResultTileItemView;
 class TileItemView;
 
-// The start page for the experimental app list.
+// The start page for the app list.
 class APP_LIST_EXPORT StartPageView : public AppListPage {
  public:
   StartPageView(AppListMainView* app_list_main_view,
                 AppListViewDelegate* view_delegate);
   ~StartPageView() override;
 
   void Reset();
 
   void UpdateForTesting();
 
@@ skipping 36 matching lines @@
   CustomLauncherPageBackgroundView*
       custom_launcher_page_background_;       // Owned by view hierarchy.
   StartPageTilesContainer* tiles_container_;  // Owned by views hierarchy.
 
   DISALLOW_COPY_AND_ASSIGN(StartPageView);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_VIEWS_START_PAGE_VIEW_H_