mash: Replace int ShelfIDs with AppLaunchID strings.

ash/public/cpp/shelf_item_delegate.cc

Index: ash/public/cpp/shelf_item_delegate.cc
diff --git a/ash/public/cpp/shelf_item_delegate.cc b/ash/public/cpp/shelf_item_delegate.cc
index 3c5fd50b8d11658e7fd21c71fe59581a30eab54c..c1fdab9f006a451c0e824c95ada958fc391d6801 100644
--- a/ash/public/cpp/shelf_item_delegate.cc
+++ b/ash/public/cpp/shelf_item_delegate.cc
@@ -6,10 +6,8 @@
 
 namespace ash {
 
-ShelfItemDelegate::ShelfItemDelegate(const ash::AppLaunchId& app_launch_id)
-    : app_launch_id_(app_launch_id),
-      shelf_id_(kInvalidShelfID),
-      image_set_by_controller_(false) {}
+ShelfItemDelegate::ShelfItemDelegate(const ash::ShelfID& shelf_id)
+    : shelf_id_(shelf_id), image_set_by_controller_(false) {}
 
 ShelfItemDelegate::~ShelfItemDelegate() {}