Add property base to the Uri class

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';
 
 // Corelib 'print' implementation.
 void _print(arg) {
   _Logger._printString(arg.toString());
 }
 
 
 class _Logger {
   static void _printString(String s) native "Logger_PrintString";
 }
 
 
 _getPrintClosure() => _print;
 
 
 void _logResolution(String msg) {
   final enabled = false;
   if (enabled) {
     _Logger._printString(msg);
   }
 }
 
 
+// Corelib 'Uri.base' implementation.
+Uri _uriBase() {
+  return new Uri.file(Directory.current.path + "/");
+}
+
+_getUriBaseClosure() => _uriBase;
+
+
 var _httpRequestResponseCode = 0;
 var _httpRequestStatusString;
 var _httpRequestResponse;
 
 _getHttpRequestResponseCode() => _httpRequestResponseCode;
 _getHttpRequestStatusString() => _httpRequestStatusString;
 _getHttpRequestResponse() => _httpRequestResponse;
 
 void _requestCompleted(List<int> data, HttpClientResponse response) {
   _httpRequestResponseCode = response.statusCode;
@@ skipping 255 matching lines @@
   }
   _logResolution('# Package: $uri -> $path');
   return path;
 }
 
 
 String _filePathFromHttpUri(Uri uri) {
   _logResolution('# Path: $uri -> $uri');
   return uri.toString();
 }