Rename blahHandler to onBlah throughout dart:io.

tests/standalone/src/DirectoryInvalidArgumentsTest.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.errorHandler = (error) {
+    d.onError = (error) {
       errors += 1;
     };
-    d.doneHandler = (completed) {
+    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());
@@ skipping 15 matching lines @@
   }
 
   static void testMain() {
     testInvalidArguments();
   }
 }
 
 main() {
   DirectoryInvalidArgumentsTest.testMain();
 }