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

mojo/public/dart/third_party/args/lib/src/utils.dart

Index: mojo/public/dart/third_party/args/lib/src/utils.dart
diff --git a/mojo/public/dart/third_party/args/lib/src/utils.dart b/mojo/public/dart/third_party/args/lib/src/utils.dart
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+// 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 args.utils;
+
+/// Pads [source] to [length] by adding spaces at the end.
+String padRight(String source, int length) =>
+    source + ' ' * (length - source.length);