Remove use of deprecated test methods (asynctTest/callbackDone/expectThrows).

Multiscript.html

Index: Multiscript.html
===================================================================
--- Multiscript.html	(revision 1080)
+++ Multiscript.html	(working copy)
@@ -12,10 +12,11 @@
 import 'Multiscript.dart';
 main() {
   useHtmlConfiguration(true);
-  asyncTest('Multiple script tags', 3, () {
+  test('Multiple script tags', () {
+    var callback = expectAsync0(() {}, count: 3);
     addHandler('done', (msg) {
       Expect.equals(msg['actual'], msg['expect']);
-      callbackDone();
+      callback();
     });
     postMessage('start', {});
   });