Replace AllAppsTileItemView with ArrowExpandView

ui/app_list/views/start_page_view.h

Index: ui/app_list/views/start_page_view.h
diff --git a/ui/app_list/views/start_page_view.h b/ui/app_list/views/start_page_view.h
index 21c51ff4b5261bdb88145a81a9e971a3d4a0033f..45e90fe6032aae1014a3d7ad8649992c85cc9c6b 100644
--- a/ui/app_list/views/start_page_view.h
+++ b/ui/app_list/views/start_page_view.h
@@ -19,6 +19,7 @@ class AppListMainView;
 class AppListView;
 class AppListViewDelegate;
 class CustomLauncherPageBackgroundView;
+class ExpandArrowView;
 class IndicatorChipView;
 class SearchResultTileItemView;
 class TileItemView;
@@ -79,6 +80,7 @@ class APP_LIST_EXPORT StartPageView : public AppListPage {
       custom_launcher_page_background_;       // Owned by views hierarchy.
   IndicatorChipView* indicator_ = nullptr;    // Owned by views hierarchy.
   StartPageTilesContainer* tiles_container_;  // Owned by views hierarchy.
+  ExpandArrowView* expand_arrow_view_ = nullptr;  // Owned by views hierarchy.
 
   const bool is_fullscreen_app_list_enabled_;