Support asynchronous main methods.

lib/src/runner/vm/isolate_listener.dart

Index: lib/src/runner/vm/isolate_listener.dart
diff --git a/lib/src/runner/vm/isolate_listener.dart b/lib/src/runner/vm/isolate_listener.dart
index ed23a1d1adfeeb67d6fe2ff89e3fc56d0e1d3f09..a25c9d682401c2243d46909f1574c2e6844d1f30 100644
--- a/lib/src/runner/vm/isolate_listener.dart
+++ b/lib/src/runner/vm/isolate_listener.dart
@@ -51,19 +51,18 @@ class IsolateListener {
     }
 
     var declarer = new Declarer();
-    try {
-      runZoned(main, zoneValues: {#test.declarer: declarer});
-    } catch (error, stackTrace) {
+    runZoned(() => new Future.sync(main), zoneValues: {
+      #test.declarer: declarer
+    }).then((_) {
+      var suite = new Suite(declarer.tests, metadata: metadata)
+          .forPlatform(TestPlatform.vm, os: currentOS);
+      new IsolateListener._(suite)._listen(sendPort);
+    }, onError: (error, stackTrace) {
       sendPort.send({
         "type": "error",
         "error": RemoteException.serialize(error, stackTrace)
       });
-      return;
-    }
-
-    var suite = new Suite(declarer.tests, metadata: metadata)
-        .forPlatform(TestPlatform.vm, os: currentOS);
-    new IsolateListener._(suite)._listen(sendPort);
+    });
   }
 
   /// Sends a message over [sendPort] indicating that the tests failed to load.