Fix resolution of packages in pub-build to allow '../../packages/foo/bar'

pkg/polymer/lib/src/build/import_inliner.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 inlines polymer-element definitions from html imports. */
 library polymer.src.build.import_inliner;
 
 import 'dart:async';
 import 'dart:convert';
 
@@ skipping 193 matching lines @@
     }
 
     if (id.path.startsWith('asset/')) {
       return 'assets/${id.package}/${id.path.substring(6)}';
     }
 
     if (primaryId.package != id.package) {
       // Techincally we shouldn't get there
       transform.logger.error("don't know how to include $id from $primaryId",
           span: span);
-      return null;
+      return href;

[Siggi Cherem (dart-lang), 2013/11/20 22:44:19]

this makes sure that we don't assign a null value on an attribute when we try to
rewrite it above. We just keep the original if we can't resolve it. (otherwise
you see the errors from these bugs:
https://code.google.com/p/dart/issues/detail?id=15012
https://code.google.com/p/dart/issues/detail?id=15083)

     }
 
     var builder = path.url;
     return builder.relative(builder.join('/', id.path),
         from: builder.join('/', builder.dirname(primaryId.path)));
   }
 }
 
 /**
  * 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
 ];