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

mojo/public/dart/third_party/mime/lib/mime.dart

+// Copyright (c) 2013, 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.
+
+/**
+ * Help for working with file format identifiers
+ * such as `text/html` and `image/png`.
+ *
+ * More details, including a list of types, are in the Wikipedia article
+ * [Internet media type](http://en.wikipedia.org/wiki/Internet_media_type).
+ * For information on installing and importing this library, see the
+ * [mime package on pub.dartlang.org]
+ * (http://pub.dartlang.org/packages/mime).
+ */
+library mime;
+
+export 'src/mime_multipart_transformer.dart';
+export 'src/mime_shared.dart';
+export 'src/mime_type.dart';