Allow arrow keys to navigate tile results in the experimental app list.

ui/app_list/views/search_result_tile_item_list_view.h

Index: ui/app_list/views/search_result_tile_item_list_view.h
diff --git a/ui/app_list/views/search_result_tile_item_list_view.h b/ui/app_list/views/search_result_tile_item_list_view.h
index 169a083277d905489999e138bade09fc6194e4c7..6d9d180023c0612b6ad2b9986afa63c8181226ae 100644
--- a/ui/app_list/views/search_result_tile_item_list_view.h
+++ b/ui/app_list/views/search_result_tile_item_list_view.h
@@ -10,6 +10,10 @@
 #include "base/macros.h"
 #include "ui/app_list/views/search_result_container_view.h"
 
+namespace views {
+class Textfield;
+}
+
 namespace app_list {
 
 class SearchResultTileItemView;
@@ -18,7 +22,7 @@ class SearchResultTileItemView;
 class APP_LIST_EXPORT SearchResultTileItemListView
     : public SearchResultContainerView {
  public:
-  SearchResultTileItemListView();
+  explicit SearchResultTileItemListView(views::Textfield* search_box);
   ~SearchResultTileItemListView() override;
 
   // Overridden from SearchResultContainerView:
@@ -34,6 +38,8 @@ class APP_LIST_EXPORT SearchResultTileItemListView
 
   std::vector<SearchResultTileItemView*> tile_views_;
 
+  views::Textfield* search_box_;  // Owned by the views hierarchy.
+
   DISALLOW_COPY_AND_ASSIGN(SearchResultTileItemListView);
 };