Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/polymer/default_build.dart

Index: observatory_pub_packages/polymer/default_build.dart
===================================================================
--- observatory_pub_packages/polymer/default_build.dart	(revision 0)
+++ observatory_pub_packages/polymer/default_build.dart	(working copy)
@@ -0,0 +1,12 @@
+// 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.
+
+/// Library that defines a main which calls build() from builder.dart. For
+/// polymer projects the build.dart file can simply export this to make the
+/// linter run on all of the entry points defined in your pubspec.yaml.
+library polymer.default_build;
+
+import 'builder.dart';
+
+main(args) { lint(options: parseOptions(args)); }