Add kernel/closed_world2_test

pkg/compiler/lib/src/universe/resolution_world_builder.dart

Index: pkg/compiler/lib/src/universe/resolution_world_builder.dart
diff --git a/pkg/compiler/lib/src/universe/resolution_world_builder.dart b/pkg/compiler/lib/src/universe/resolution_world_builder.dart
index 6eaf10427ee0d2689ec3887b4fea41e1654bca7e..5238ec5ad4c6c10146f55296f7bb59cc1447ff3a 100644
--- a/pkg/compiler/lib/src/universe/resolution_world_builder.dart
+++ b/pkg/compiler/lib/src/universe/resolution_world_builder.dart
@@ -785,3 +785,24 @@ abstract class ResolutionWorldBuilderBase
     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');
+  }
+}