Removing polymer-specific code from barback runner

pkg/observe/lib/transformer.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.
 
 /**
  * Code transform for @observable. The core transformation is relatively
  * straightforward, and essentially like an editor refactoring.
  */
 library observe.transformer;
 
@@ skipping 10 matching lines @@
 /**
  * A [Transformer] that replaces observables based on dirty-checking with an
  * implementation based on change notifications.
  *
  * The transformation adds hooks for field setters and notifies the observation
  * system of the change.
  */
 class ObservableTransformer extends Transformer {
 
   final List<String> _files;
-  ObservableTransformer() : _files = null;
+  ObservableTransformer([List<String> files]) : _files = files;
   ObservableTransformer.asPlugin(BarbackSettings settings)
       : _files = _readFiles(settings.configuration['files']);
 
   static List<String> _readFiles(value) {
     if (value == null) return null;
     var files = [];
     bool error;
     if (value is List) {
       files = value;
       error = value.any((e) => e is! String);
@@ skipping 388 matching lines @@
 
 Token _findFieldSeperator(Token token) {
   while (token != null) {
     if (token.type == TokenType.COMMA || token.type == TokenType.SEMICOLON) {
       break;
     }
     token = token.next;
   }
   return token;
 }