Fix for URI resolution w/ file scheme set in package map.

pkg/analyzer/lib/src/generated/source.dart

 // Copyright (c) 2014, 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.source;
 
 import 'dart:collection';
@@ skipping 800 matching lines @@
       if (containingSource == null) {
         throw new AnalysisException(
             "Cannot resolve a relative URI without a containing source: $containedUri");
       }
       containedUri = containingSource.resolveRelativeUri(containedUri);
     }
     // Now check .packages.
     if (_packages != null && containedUri.scheme == 'package') {
       Uri packageUri =
           _packages.resolve(containedUri, notFound: (Uri packageUri) => null);
-      //TODO(pquitslund): package_config needs to be updated to set schemes for file URIs.
+      // Ensure scheme is set.
       if (packageUri != null && packageUri.scheme == '') {
-        containedUri = packageUri.replace(scheme: 'file');
+        packageUri = packageUri.replace(scheme: 'file');
       }
+      containedUri = packageUri;
     }
     for (UriResolver resolver in _resolvers) {
       Source result = resolver.resolveAbsolute(containedUri);
       if (result != null) {
         return result;
       }
     }
     return null;
   }
 }
@@ skipping 232 matching lines @@
 
   /**
    * Return an absolute URI that represents the given source, or `null` if a valid URI cannot
    * be computed.
    *
    * @param source the source to get URI for
    * @return the absolute URI representing the given source
    */
   Uri restoreAbsolute(Source source) => null;
 }