Add error handling to directory

tests/standalone/src/io/DirectoryInvalidArgumentsTest.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.
 
 #import("dart:io");
 
 class DirectoryInvalidArgumentsTest {
   static void testFailingList(Directory d, var recursive) {
     int errors = 0;
     d.onError = (error) {
       errors += 1;
     };
     d.onDone = (completed) {
       Expect.equals(1, errors);
       Expect.isFalse(completed);
     };
     Expect.equals(0, errors);
     d.list(recursive);
   }
 
   static void testInvalidArguments() {
     Directory d = new Directory(12);
-    Expect.isFalse(d.existsSync());
+    try {
+      d.existsSync();
+      Expect.fail("No exception thrown");
+    } catch (var e) {
+      Expect.isTrue(e is IllegalArgumentException);
+    }
     try {
       d.deleteSync();
       Expect.fail("No exception thrown");
     } catch (var e) {
-      Expect.isTrue(e is DirectoryException);
+      Expect.isTrue(e is IllegalArgumentException);
     }
     try {
       d.createSync();
       Expect.fail("No exception thrown");
     } catch (var e) {
-      Expect.isTrue(e is DirectoryException);
+      Expect.isTrue(e is IllegalArgumentException);
     }
     testFailingList(d, false);
     d = new Directory(".");
     testFailingList(d, 1);
   }
 
   static void testMain() {
     testInvalidArguments();
   }
 }
 
 main() {
   DirectoryInvalidArgumentsTest.testMain();
 }