Stop running pub get at gclient sync time and fix build bugs

mojo/public/dart/third_party/shelf/lib/shelf.dart

Index: mojo/public/dart/third_party/shelf/lib/shelf.dart
diff --git a/mojo/public/dart/third_party/shelf/lib/shelf.dart b/mojo/public/dart/third_party/shelf/lib/shelf.dart
new file mode 100644
index 0000000000000000000000000000000000000000..98d7815182f716458598df8134fa003cefc1b043
--- /dev/null
+++ b/mojo/public/dart/third_party/shelf/lib/shelf.dart
@@ -0,0 +1,14 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library shelf;
+
+export 'src/cascade.dart';
+export 'src/handler.dart';
+export 'src/handlers/logger.dart';
+export 'src/hijack_exception.dart';
+export 'src/middleware.dart';
+export 'src/pipeline.dart';
+export 'src/request.dart';
+export 'src/response.dart';