Change File.directory to not do any IO

utils/compiler/create_snapshot.dart

 // Copyright (c) 2013, 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.
 
 import 'dart:io';
 
 Future<String> getVersion(var options, var rootPath) {
   var os = Platform.operatingSystem;
   var suffix = os == 'windows' ? '.exe' : '';
   var checkedInBinary =
@@ skipping 64 matching lines @@
     var argumentSplit = argument.split("=");
     if (argumentSplit.length != 2) throw "Invalid argument $argument, no =";
     if (!validArguments.contains(argumentSplit[0])) {
       throw "Invalid argument $argument";
     }
     args[argumentSplit[0].substring(2)] = argumentSplit[1];
   }
   if (!args.containsKey("dart2js_main")) throw "Please specify dart2js_main";
   if (!args.containsKey("output_dir")) throw "Please specify output_dir";
 
-  var scriptFile = new File(options.script);
-  var path = new Path(scriptFile.directorySync().path);
+  var scriptFile = new File(new File(options.script).fullPathSync());
+  var path = new Path(scriptFile.directory.path);
   var rootPath = path.directoryPath.directoryPath;
-
   getSnapshotGenerationFile(options, args, rootPath).then((result) {
     var wrapper = "${args['output_dir']}/utils_wrapper.dart";
     writeSnapshotFile(wrapper, result);
     createSnapshot(options, wrapper);
   });
 }