Factor out the anchor prefix to easily allow switching to #!

client/web/typedef.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.
 
 library web.typedef;
 
 import 'package:dartdoc_viewer/item.dart';
+import 'package:dartdoc_viewer/location.dart';
 import 'package:polymer/polymer.dart';
 import 'member.dart';
 
 @CustomTag("dartdoc-typedef")
 class TypedefElement extends MemberElement {
   TypedefElement.created() : super.created();
 
   wrongClass(newItem) => newItem is! Typedef;
   get defaultItem => _defaultItem;
   static final _defaultItem =
       new Typedef({'name' : 'loading', 'qualifiedName' : 'loading'});
+
+  String get prefixedLocation => locationPrefixed(item.type.location);
 }