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

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 10 matching lines @@
  * This transformer assumes that all script tags point to external files. To
  * support script tags with inlined code, use this transformer after running
  * [InlineCodeExtractor] on an earlier phase.
  *
  * 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 {
-  /** Only run this transformer on .html files. */
-  final String allowedExtensions = ".html";
+  /** Only run on entry point .html files. */
+  Future<bool> isPrimary(Asset input) => isPrimaryHtml(input.id);
 
   Future apply(Transform transform) {
     var id = transform.primaryInput.id;
     var logger = transform.logger;
     return transform.primaryInput.readAsString().then((content) {
-      var document = parseHtml(content, id.path, logger);
+      var document = parseHtml(content, id.path, logger,
+          checkDocType: false);
       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 87 matching lines @@
 
 void main() {
   initPolymer([
 """;
 
 // TODO(sigmund): investigate alternative to get the baseUri (dartbug.com/12612)
 const _mainSuffix = """
     ], currentMirrorSystem().isolate.rootLibrary.uri.toString());
 }
 """;