Roll Observatory packages and add a roll script

packages/polymer/lib/src/loader.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.
 
 part of polymer;
 
 /// Initializes a polymer application as follows:
 ///   * if running in development mode, set up a dirty-checking zone that polls
 ///     for observable changes
 ///   * initialize template binding and polymer-element
@@ skipping 149 matching lines @@
     // Only alert once per waiting state.
     if (lastAlert == lastWaiting) return;
     lastAlert = lastWaiting;
 
     print('No elements registered in a while, but still waiting on '
         '${waiting.length} elements to be registered. Check that you have a '
         'class with an @CustomTag annotation for each of the following tags: '
         '${waiting.map((e) => "'${e.attributes['name']}'").join(', ')}');
   });
 }