Switch web_ui to use path 1.0.0

lib/src/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.
 
 library web_ui.src.utils;
 
 import 'dart:async';
 
-import 'package:path/path.dart' show Builder;
+import 'package:path/path.dart' show Context;
 
 
 /**
  * An instance of the path library builder. We could just use the default
  * builder in path, but we add this indirection to make it possible to run
  * unittest for windows paths.
  */
-Builder path = new Builder();
+Context path = new Context();
 
 /** Convert a OS specific path into a url. */
 String pathToUrl(String relPath) =>
   (path.separator == '/') ? relPath : path.split(relPath).join('/');
 
 /**
  * Converts a string name with hyphens into an identifier, by removing hyphens
  * and capitalizing the following letter. Optionally [startUppercase] to
  * captialize the first letter.
  */
@@ skipping 269 matching lines @@
     if (message != null) {
       additionalMessage = '\nInternal message: $message';
     }
     return "We're sorry, you've just found a compiler bug. "
       'You can report it at:\n'
       'https://github.com/dart-lang/web-ui/issues/new\n'
       'Thanks in advance for the bug report! It will help us improve Web UI.'
       '$additionalMessage';
   }
 }