Revert "Simplify and fix implicit closure check, speed up Closure_equals"

tests/isolate/message4_test.dart

-// Copyright (c) 2017, 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.
-
-// Dart test program for testing serialization of messages with static
-// native functions.
-
-library MessageTest;
-
-import 'dart:async';
-import 'dart:collection';
-import 'dart:isolate';
-import 'package:async_helper/async_helper.dart';
-import 'package:expect/expect.dart';
-
-void echoMain(msg) {
-  SendPort replyTo = msg[0];
-  SendPort pong = msg[1];
-  ReceivePort port = new ReceivePort();
-  replyTo.send(port.sendPort);
-  port.listen((msg) {
-    if (msg == "halt") {
-      port.close();
-    } else {
-      pong.send(msg);
-    }
-  });
-}
-
-void runTests(SendPort ping, Queue checks) {
-  ping.send("abc");
-  checks.add((x) => Expect.equals("abc", x));
-
-  ping.send(int.parse);
-  checks.add((x) => Expect.identical(int.parse, x));
-
-  ping.send(identityHashCode);
-  checks.add((x) => Expect.identical(identityHashCode, x));
-
-  ping.send(identical);
-  checks.add((x) => Expect.identical(identical, x));
-}
-
-void main() async {
-  asyncStart();
-  Queue checks = new Queue();
-  ReceivePort testPort = new ReceivePort();
-  Completer completer = new Completer();
-
-  testPort.listen((msg) {
-    Function check = checks.removeFirst();
-    check(msg);
-    if (checks.isEmpty) {
-      completer.complete();
-      testPort.close();
-    }
-  });
-
-  ReceivePort initialReplyPort = new ReceivePort();
-
-  Isolate i = await Isolate
-      .spawn(echoMain, [initialReplyPort.sendPort, testPort.sendPort]);
-  SendPort ping = await initialReplyPort.first;
-  runTests(ping, checks);
-  Expect.isTrue(checks.length > 0);
-  await completer.future;
-  ping.send("halt");
-  asyncEnd();
-}