Adding check or trust type checks to builder_kernel.dart.

tests/compiler/dart2js/kernel/assert_test.dart

 // Copyright (c) 2016, 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.
 
 import 'package:compiler/src/commandline_options.dart' show Flags;
 import 'package:test/test.dart';
 
 import 'helper.dart' show check;
 
 main() {
   test('assert without message', () {
     String code = '''
 bool foo() => 2 + 2 == 4;
 main() {
   assert(foo());
 }''';
     return check(code, extraOptions: const <String>[Flags.enableCheckedMode]);
   });
 
   test('assert with message', () {
     String code = '''
 bool foo() => 2 + 2 == 4;
 main() {
   assert(foo(), "foo failed");
 }''';
     return check(code,
-        // disable type inference because kernel doesn't yet support
-        // checked mode type checks
-        disableTypeInference: false,
         extraOptions: const <String>[
           Flags.enableCheckedMode,
           Flags.enableAssertMessage,
         ]);
   });
 }