Fix Kernel tests

pkg/kernel/test/baseline_strong_mode_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:kernel/class_hierarchy.dart';
 import 'package:kernel/core_types.dart';
 import 'package:kernel/kernel.dart';
 import 'package:kernel/transformations/insert_covariance_checks.dart';
 import 'package:kernel/transformations/insert_type_checks.dart';
 import 'package:kernel/transformations/mixin_full_resolution.dart';
 import 'package:kernel/transformations/treeshaker.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> performModularTransformations(Program program) {
+    new MixinFullResolution().transform(program);
+    return const <String>[];
+  }
+
+  @override
+  List<String> performGlobalTransformations(Program program) {
     List<String> errors = <String>[];
-    new MixinFullResolution().transform(program);
     new InsertTypeChecks().transformProgram(program);
     new InsertCovarianceChecks().transformProgram(program);
     new TestTypeChecker(
             errors, new CoreTypes(program), new ClassHierarchy(program))
         .checkProgram(program);
     new TreeShaker(program, strongMode: true).transform(program);
     program.accept(new TreeShakerCheck());
     return errors;
   }
 }
@@ skipping 31 matching lines @@
       throw 'Code not tree-shaken at ${node.location}.\n'
           'The string literal $node is used to indicate that the code is '
           'expected to be removed by strong-mode tree shaking';
     }
   }
 }
 
 void main() {
   runBaselineTests('strong-mode', new StrongModeTest());
 }