Fix error in processing dart-ext urls with a relative path.

runtime/bin/builtin.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 builtin;
 import 'dart:io';
 import 'dart:async';
 // import 'root_library'; happens here from C Code
 
 // The root library (aka the script) is imported into this library. The
@@ skipping 225 matching lines @@
 String _filePathFromUri(String userUri) {
   var uri = Uri.parse(userUri);
   _logResolution('# Getting file path from: $uri');
 
   var path;
   switch (uri.scheme) {
     case '':
     case 'file':
       return uri.toFilePath();
       break;
     case 'dart-ext':

[Søren Gjesse, 2014/01/27 20:57:51]

This should just be

  new Uri.file(uri.path)

that should take care of the relative/absolute path.

Also shouldn't we check that the host is empty? Don't think we want to load
extensions from a file server.

-      return new Uri(scheme: 'file',
+      // Relative file URIs don't start with file:///.
+      var scheme = (uri.path.startsWith('/') ? 'file' : '');
+      return new Uri(scheme: scheme,
                      host: uri.host,
                      path: uri.path).toFilePath();
       break;
     case 'package':
       return _filePathFromPackageUri(uri);
       break;
     case 'http':
       return uri.toString();
     default:
       // Only handling file, dart-ext, http, and package URIs
@@ skipping 12 matching lines @@
 
     throw "URIs using the 'package:' scheme should look like "
           "'$right', not '$wrong'.";
   }
 
   var packageRoot = _packageRoot == null ?
                     _entryPointScript.resolve('packages/') :
                     _packageRoot;
   return _filePathFromUri(packageRoot.resolve(uri.path).toString());
 }