Update shelf_static and enable directory listing

packages/flutter_tools/bin/sky_server.dart

@@ -37,7 +37,7 @@ main(List<String> argv) async {
   }
 
   Handler handler = createStaticHandler(Directory.current.path,
-      serveFilesOutsidePath: true);
+      serveFilesOutsidePath: true, listDirectories: true);
 
   if (args['verbose'])
     handler = const Pipeline().addMiddleware(logRequests()).addHandler(handler);

packages/flutter_tools/pubspec.yaml

@@ -2,7 +2,7 @@ author: Chromium Authors <sky-dev@googlegroups.com>
 dependencies:
   args: ^0.13.0
   shelf: ^0.6.2
-  shelf_static: ^0.2.2
+  shelf_static: ^0.2.3
 description: Tools for building Sky applications
 environment:
   sdk: ">=1.8.0 <2.0.0"