Add kernel/closed_world2_test

pkg/compiler/lib/src/universe/resolution_world_builder.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.
 
 part of world_builder;
 
 abstract class ResolutionWorldBuilder implements WorldBuilder, OpenWorld {
   /// Set of all local functions in the program. Used by the mirror tracking
   /// system to find all live closure instances.
   Iterable<Local> get localFunctions;
@@ skipping 767 matching lines @@
   @override
   bool isMemberUsed(MemberEntity member) {
     if (member.isInstanceMember) {
       _MemberUsage usage = _instanceMemberUsage[member];
       if (usage != null && usage.hasUse) return true;
     }
     _StaticMemberUsage usage = _staticMemberUsage[member];
     return usage != null && usage.hasUse;
   }
 }
+
+class KernelResolutionWorldBuilder extends ResolutionWorldBuilderBase {
+  KernelResolutionWorldBuilder(
+      ElementEnvironment elementEnvironment,
+      CommonElements commonElements,
+      NativeBasicData nativeBasicData,
+      SelectorConstraintsStrategy selectorConstraintsStrategy)
+      : super(elementEnvironment, commonElements, nativeBasicData,
+            selectorConstraintsStrategy);
+
+  @override
+  ClosedWorld closeWorld(DiagnosticReporter reporter) {
+    // TODO(johnniwinther): Implement this.
+    return null;

[Emily Fortuna, 2017/04/10 19:50:58]

throw instead?

[Johnni Winther, 2017/04/11 07:58:58]

This is called at the end of the test in computeClosedWorld so throwing doesn't
work.

+  }
+
+  @override
+  void registerClass(ClassEntity cls) {
+    throw new UnimplementedError('KernelResolutionWorldBuilder.registerClass');
+  }
+}