Make event-handlers edge-triggered and move socket-state to Dart.

tests/standalone/io/http_response_deadline_test.dart

Index: tests/standalone/io/http_response_deadline_test.dart
diff --git a/tests/standalone/io/http_response_deadline_test.dart b/tests/standalone/io/http_response_deadline_test.dart
index 5f537936583ce3ae124dc2d0646dd50d3ff36ee6..e10913ab076051b5e67acc04a7b1985e871e8919 100644
--- a/tests/standalone/io/http_response_deadline_test.dart
+++ b/tests/standalone/io/http_response_deadline_test.dart
@@ -63,6 +63,7 @@ void testDeadlineAndDetach(int connections) {
         new Timer(const Duration(milliseconds: 100), () {
           socket.write('stuff');
           socket.close();
+          socket.listen(null);
         });
       });
     });