Add a unit test for resetting the app list on a reshow.

ui/app_list/views/test/apps_grid_view_test_api.cc

Index: ui/app_list/views/test/apps_grid_view_test_api.cc
diff --git a/ui/app_list/views/test/apps_grid_view_test_api.cc b/ui/app_list/views/test/apps_grid_view_test_api.cc
index b87ef28a845a577ef4941530b0aee888dde5267b..5e425c384884f014fad91a104c696b8327309c97 100644
--- a/ui/app_list/views/test/apps_grid_view_test_api.cc
+++ b/ui/app_list/views/test/apps_grid_view_test_api.cc
@@ -4,7 +4,9 @@
 
 #include "ui/app_list/views/test/apps_grid_view_test_api.h"
 
+#include "ui/app_list/views/app_list_item_view.h"
 #include "ui/app_list/views/apps_grid_view.h"
+#include "ui/events/event.h"
 
 namespace app_list {
 namespace test {
@@ -29,5 +31,10 @@ void AppsGridViewTestApi::SetPageFlipDelay(int page_flip_delay_in_ms) {
   view_->page_flip_delay_in_ms_ = page_flip_delay_in_ms;
 }
 
+void AppsGridViewTestApi::PressItemAt(int index) {
+  GetViewAtModelIndex(index)->OnKeyPressed(
+      ui::KeyEvent(ui::ET_KEY_PRESSED, ui::VKEY_RETURN, 0, false));
+}
+
 }  // namespace test
 }  // namespace app_list