Revert "Fix strong mode errors in dart:io."

tests/standalone/io/https_bad_certificate_test.dart

 // Copyright (c) 2013, 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.
 
 // This test verifies that the bad certificate callback works in HttpClient.
 
 import "dart:async";
 import "dart:io";
 
 import "package:expect/expect.dart";
@@ skipping 53 matching lines @@
     return callbackReturns;
   };
 
   try {
     var request = await client.getUrl(Uri.parse('https://$HOST_NAME:$port/'));
     Expect.equals('pass', result);
     await request.close();
   } catch (error) {
     Expect.notEquals(result, 'pass');
     if (result == 'fail') {
-      Expect.isTrue(error is HandshakeException ||
-          (callbackReturns is! bool && error is TypeError));
+      Expect.isTrue(error is HandshakeException);
     } else if (result == 'throw') {
       Expect.isTrue(error is CustomException);
     } else {
       Expect.fail('Unknown expectation $result');
     }
   }
 }