Add data-URI support class to dart:core (next to Uri).

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;
 // NOTE: Do not import 'dart:io' in builtin.
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_internal';
 import 'dart:isolate';
@@ skipping 26 matching lines @@
 
 
 // Corelib 'Uri.base' implementation.
 // Uri.base is susceptible to changes in the current working directory.
 _getCurrentDirectoryPath() native "Builtin_GetCurrentDirectory";
 
 
 Uri _uriBase() {
   // We are not using Dircetory.current here to limit the dependency
   // on dart:io. This code is the same as:
-  //   return new Uri.file(Directory.current.path + "/");
-  var result = _getCurrentDirectoryPath();
-  return new Uri.file("$result/");
+  //   return new Uri.directory(Directory.current.path);
+  var path = _getCurrentDirectoryPath();
+  return new Uri.directory(path);
 }
 
 
 _getUriBaseClosure() => _uriBase;
 
 
 // Asynchronous loading of resources.
 // The embedder forwards most loading requests to this library.
 
 // See Dart_LibraryTag in dart_api.h
@@ skipping 767 matching lines @@
 }
 
 
 // Register callbacks and hooks with the rest of the core libraries.
 _setupHooks() {
   _setupCompleted = true;
   VMLibraryHooks.resourceReadAsBytes = _resourceReadAsBytes;
   VMLibraryHooks.getPackageRoot = _getPackageRoot;
   VMLibraryHooks.getPackageMap = _getPackageMap;
 }