mash: Replace int ShelfIDs with AppLaunchID strings.

ash/shelf/shelf_tooltip_manager_unittest.cc

Index: ash/shelf/shelf_tooltip_manager_unittest.cc
diff --git a/ash/shelf/shelf_tooltip_manager_unittest.cc b/ash/shelf/shelf_tooltip_manager_unittest.cc
index 089e998b37c6b9fca180b4d8984002fdd66434d4..4512bdb611e5c0c09893d0405f8ff8345c9c39fe 100644
--- a/ash/shelf/shelf_tooltip_manager_unittest.cc
+++ b/ash/shelf/shelf_tooltip_manager_unittest.cc
@@ -85,6 +85,7 @@ TEST_F(ShelfTooltipManagerTest, DoNotShowForInvalidView) {
   // The manager should start the timer for a view on the shelf.
   ShelfModel* model = shelf_view_->model();
   ShelfItem item;
+  item.id = ShelfID("foo");
   item.type = TYPE_PINNED_APP;
   const int index = model->Add(item);
   // Note: There's no easy way to correlate shelf a model index/id to its view.