Re-enable kernel unit tests on platforms where they are supported.

pkg/kernel/test/baseline_strong_mode_test_disabled.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:kernel/class_hierarchy.dart';
-import 'package:kernel/core_types.dart';
-import 'package:kernel/kernel.dart';
-import 'package:kernel/transformations/mixin_full_resolution.dart';
-import 'package:kernel/type_checker.dart';
-import 'package:path/path.dart' as pathlib;
-
-import 'baseline_tester.dart';
-
-class StrongModeTest extends TestTarget {
-  @override
-  List<String> get extraRequiredLibraries => [];
-
-  @override
-  String get name => 'strong-mode-test';
-
-  @override
-  bool get strongMode => true;
-
-  @override
-  List<String> transformProgram(Program program) {
-    List<String> errors = <String>[];
-    new MixinFullResolution().transform(program);
-    new TestTypeChecker(
-            errors, new CoreTypes(program), new ClassHierarchy(program))
-        .checkProgram(program);
-    return errors;
-  }
-}
-
-class TestTypeChecker extends TypeChecker {
-  final List<String> errors;
-
-  TestTypeChecker(this.errors, CoreTypes coreTypes, ClassHierarchy hierarchy)
-      : super(coreTypes, hierarchy);
-
-  @override
-  void checkAssignable(TreeNode where, DartType from, DartType to) {
-    if (!environment.isSubtypeOf(from, to)) {
-      fail(where, '$from is not a subtype of $to');
-    }
-  }
-
-  @override
-  void fail(TreeNode where, String message) {
-    var location = where.location;
-    var locationString;
-    if (location != null) {
-      var file = pathlib.basename(Uri.parse(location.file).path);
-      locationString = '($file:${location.line}:${location.column})';
-    } else {
-      locationString = '(no location)';
-    }
-    errors.add('$message $locationString');
-  }
-}
-
-void main() {
-  runBaselineTests('strong-mode', new StrongModeTest());
-}