Make Transform a little more pleasant to use:

pkg/polymer/lib/src/transform/script_compactor.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 combines multiple dart script tags into a single one. */
 library polymer.src.transform.script_compactor;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
@@ skipping 14 matching lines @@
  * Internally, this transformer will convert each script tag into an import
  * statement to a library, and then uses `initPolymer` (see polymer.dart)  to
  * invoke the main method on each of these libraries and register any polymer
  * elements annotated with `@CustomTag`.
  */
 class ScriptCompactor extends Transformer {
   Future<bool> isPrimary(Asset input) =>
       new Future.value(input.id.extension == ".html");
 
   Future apply(Transform transform) {
-    var id = transform.primaryId;
+    var id = transform.primaryInput.id;
     var logger = transform.logger;
-    return getPrimaryContent(transform).then((content) {
+    return transform.primaryInput.readAsString().then((content) {
       var document = parseHtml(content, id.path, logger);
       var libraries = [];
       bool changed = false;
       var dartLoaderTag = null;
       for (var tag in document.queryAll('script')) {
         var src = tag.attributes['src'];
         if (src != null) {
           if (src == 'packages/polymer/boot.js') {
             tag.remove();
             continue;
@@ skipping 56 matching lines @@
 
   /**
    * Generate the import url for a file described by [id], referenced by a file
    * with [sourceId].
    */
   String importUrlFor(AssetId id, AssetId sourceId, TransformLogger logger) {
     // use package: urls if possible
     if (id.path.startsWith('lib/')) {
       return 'package:${id.package}/${id.path.substring(4)}';
     }
-    
+
     // Use relative urls only if it's possible.
     if (id.package != sourceId.package) {
       logger.error("don't know how to import $id from $sourceId");
       return null;
     }
 
     var builder = path.url;
     return builder.relative(builder.join('/', id.path),
         from: builder.join('/', builder.dirname(sourceId.path)));
   }
@@ skipping 11 matching lines @@
 
 void main() {
   initPolymer([
 """;
 
 // TODO(sigmund): investigate alternative to get the baseUri (dartbug.com/12612)
 const _mainSuffix = """
     ], currentMirrorSystem().isolate.rootLibrary.uri.toString());
 }
 """;