Add keyboard navigation to the custom launcher page on app list start page.

ui/app_list/app_list_model.h

Index: ui/app_list/app_list_model.h
diff --git a/ui/app_list/app_list_model.h b/ui/app_list/app_list_model.h
index 56e349c4bbe86048a7f6755900047ffc95937e6d..8881a74f302018364d155d7e437416ca3c0edf4a 100644
--- a/ui/app_list/app_list_model.h
+++ b/ui/app_list/app_list_model.h
@@ -135,6 +135,14 @@ class APP_LIST_EXPORT AppListModel : public AppListItemListObserver {
     return custom_launcher_page_enabled_;
   }
 
+  void set_custom_launcher_page_name(const std::string& name) {
+    custom_launcher_page_name_ = name;
+  }
+
+  const std::string& custom_launcher_page_name() const {
+    return custom_launcher_page_name_;
+  }
+
   // Pushes a custom launcher page's subpage into the state stack in the model.
   void PushCustomLauncherPageSubpage();
 
@@ -208,6 +216,7 @@ class APP_LIST_EXPORT AppListModel : public AppListItemListObserver {
   ObserverList<AppListModelObserver, true> observers_;
   bool folders_enabled_;
   bool custom_launcher_page_enabled_;
+  std::string custom_launcher_page_name_;
   bool search_engine_is_google_;
 
   // The current number of subpages the custom launcher page has pushed.