Make Transform a little more pleasant to use:

pkg/polymer/lib/src/transform/code_extractor.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.
 
 /** Transfomer that extracts inlined script code into separate assets. */
 library polymer.src.transformers;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:path/path.dart' as path;
 
 import 'common.dart';
 
 /**
  * Transformer that extracts Dart code inlined in HTML script tags and outputs a
  * separate file for each.
  */
 class InlineCodeExtractor extends Transformer {
   Future<bool> isPrimary(Asset input) =>
       new Future.value(input.id.extension == ".html");
 
   Future apply(Transform transform) {
-    var inputId = transform.primaryId;
-    return getPrimaryContent(transform).then((content) {
+    var inputId = transform.primaryInput.id;
+    return transform.primaryInput.readAsString().then((content) {
       var document = parseHtml(content, inputId.path, transform.logger);
       int count = 0;
       bool htmlChanged = false;
       for (var tag in document.queryAll('script')) {
         // Only process tags that have inline Dart code
         if (tag.attributes['type'] != 'application/dart' ||
           tag.attributes.containsKey('src')) {
           continue;
         }
         htmlChanged = true;
@@ skipping 13 matching lines @@
         var id = inputId.addExtension('.$count.dart');
         transform.addOutput(new Asset.fromString(id, textContent.value));
         textContent.remove();
         count++;
       }
       transform.addOutput(new Asset.fromString(inputId,
           htmlChanged ? document.outerHtml : content));
     });
   }
 }