Implement methods in KernelClosedWorldMixin

pkg/compiler/lib/src/kernel/element_map_impl.dart

Index: pkg/compiler/lib/src/kernel/element_map_impl.dart
diff --git a/pkg/compiler/lib/src/kernel/element_map_impl.dart b/pkg/compiler/lib/src/kernel/element_map_impl.dart
index d270bb60c38c482bfdd88814b280e38c4d6b4a49..8437fe8f7ab200849ff3ea9817ce8b4567448e81 100644
--- a/pkg/compiler/lib/src/kernel/element_map_impl.dart
+++ b/pkg/compiler/lib/src/kernel/element_map_impl.dart
@@ -1595,18 +1595,18 @@ abstract class KernelClosedWorldMixin implements ClosedWorldBase {
 
   @override
   bool isNamedMixinApplication(ClassEntity cls) {
-    throw new UnimplementedError(
-        'KernelClosedWorldMixin.isNamedMixinApplication');
+    return elementMap._isMixinApplication(cls) &&
+        elementMap._isUnnamedMixinApplication(cls);
   }
 
   @override
   ClassEntity getAppliedMixin(ClassEntity cls) {
-    throw new UnimplementedError('KernelClosedWorldMixin.getAppliedMixin');
+    return elementMap._getAppliedMixin(cls);
   }
 
   @override
   Iterable<ClassEntity> getInterfaces(ClassEntity cls) {
-    throw new UnimplementedError('KernelClosedWorldMixin.getInterfaces');
+    return elementMap._getInterfaces(cls).map((t) => t.element);
   }
 
   @override