Another case of the VM getting a path into Uri.parse.

runtime/bin/builtin.dart

Index: runtime/bin/builtin.dart
diff --git a/runtime/bin/builtin.dart b/runtime/bin/builtin.dart
index 3931c5947b1ea460e2c9cedd2d1bab1da2f46d1d..ad5c7edc2fdf67562e57a847524bce0d1833ba1c 100644
--- a/runtime/bin/builtin.dart
+++ b/runtime/bin/builtin.dart
@@ -362,7 +362,7 @@ void _loadLibrarySource(tag, uri, libraryUri, text) {
 // Asynchronously loads source code through an http or file uri.
 _loadSourceAsync(int tag, String uri, String libraryUri) {
   var filePath = _filePathFromUri(uri);
-  Uri sourceUri = new Uri.file(filePath);
+  Uri sourceUri = _uriFromPathOrUri(filePath);
   _numOutstandingLoadRequests++;
   _logResolution("_loadLibrarySource($uri), "
                  "${_numOutstandingLoadRequests} requests outstanding");