Apply several phases only to entrypoint files (which currently are identified as

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:analyzer_experimental/src/generated/ast.dart';
 import 'package:analyzer_experimental/src/generated/error.dart';
 import 'package:analyzer_experimental/src/generated/parser.dart';
 import 'package:analyzer_experimental/src/generated/scanner.dart';
 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 {
   /** Only run this transformer on .html files. */
   final String allowedExtensions = ".html";
 
-
   Future apply(Transform transform) {
     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')) {
@@ skipping 33 matching lines @@
   var errorListener = new _ErrorCollector();
   var token = new StringScanner(null, code, errorListener).tokenize();
   var unit = new Parser(null, errorListener).parseCompilationUnit(token);
   return unit.directives.any((d) => d is LibraryDirective);
 }
 
 class _ErrorCollector extends AnalysisErrorListener {
   final errors = <AnalysisError>[];
   onError(error) => errors.add(error);
 }