Allow changing a file from a part to a library.

lib/src/codegen/html_codegen.dart

 // Copyright (c) 2015, 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.
 
 library dev_compiler.src.codegen.html_codegen;
 
 import 'package:html5lib/dom.dart';
 import 'package:html5lib/parser.dart' show parseFragment;
 import 'package:logging/logging.dart' show Logger;
 
@@ skipping 25 matching lines @@
         'unexpected script. Only one Dart script tag allowed '
         '(see https://github.com/dart-lang/dart-dev-compiler/issues/53).',
         color: options.useColors ? colorOf('warning') : false));
     s.remove();
   });
 
   if (options.outputDart) return '${document.outerHtml}\n';
 
   var libraries = [];
   visitInPostOrder(root, (n) {
-    if (n is LibrarySourceNode) libraries.add(n);
-  });
+    if (n is DartSourceNode) libraries.add(n);
+  }, includeParts: false);
 
   String mainLibraryName;
   var fragment = _loadRuntimeScripts();
   if (!options.checkSdk) fragment.nodes.add(_miniMockSdk);
   for (var lib in libraries) {
     var info = lib.info;
     if (info == null) continue;
     if (info.isEntry) mainLibraryName = jsLibraryName(info.library);
     fragment.nodes.add(_libraryInclude(jsOutputPath(info, root.uri)));
   }
@@ skipping 21 matching lines @@
 /// some small samples.
 // TODO(sigmund,jmesserly): remove.
 Node get _miniMockSdk => parseFragment('''
 <script>
   /* placehorder for unimplemented code libraries */
   var math = Math;
   var core = { int: { parse: Number }, print: e => console.log(e) };
   var dom = { document: document };
 </script>''');
 final _log = new Logger('dev_compiler.src.codegen.html_codegen');