Prune the old deploy code. This CL does a few changes:

pkg/polymer/lib/src/html5_utils.dart

-// Copyright (c) 2012, 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.
-
-// TODO(jmesserly): html5lib might be a better home for this.
-// But at the moment we only need it here.
-
-library html5_utils;
-
-/**
- * HTML attributes that expect a URL value.
- * <http://dev.w3.org/html5/spec/section-index.html#attributes-1>
- *
- * Every one of these attributes is a URL in every context where it is used in
- * the DOM. The comments show every DOM element where an attribute can be used.
- */
-const urlAttributes = const [
-  'action',     // in form
-  'background', // in body
-  'cite',       // in blockquote, del, ins, q
-  'data',       // in object
-  'formaction', // in button, input
-  'href',       // in a, area, link, base, command
-  'icon',       // in command
-  'manifest',   // in html
-  'poster',     // in video
-  'src',        // in audio, embed, iframe, img, input, script, source, track,
-                //    video
-];