Remove implementations of mirror methods not in the API from the VM. Update tests.

tests/compiler/dart2js/message_kind_test.dart

Index: tests/compiler/dart2js/message_kind_test.dart
diff --git a/tests/compiler/dart2js/message_kind_test.dart b/tests/compiler/dart2js/message_kind_test.dart
index 6610e125cbd2bdc4d4d6dbb99ddc7b86d533b426..505fe5b3da594e8c447dc6f672a703f0fd1dd02c 100644
--- a/tests/compiler/dart2js/message_kind_test.dart
+++ b/tests/compiler/dart2js/message_kind_test.dart
@@ -16,7 +16,9 @@ import 'dart:mirrors';
 main() {
   ClassMirror cls = reflectClass(MessageKind);
   Map<String, MessageKind> kinds = <String, MessageKind>{};
-  cls.variables.forEach((Symbol name, VariableMirror variable) {
+  cls.declarations.forEach((Symbol name, DeclarationMirror declaration) {
+    if (declaration is! VariableMirror) return;
+    VariableMirror variable = declaration;
     if (variable.isStatic) {
       var value = cls.getField(name).reflectee;
       if (value is MessageKind) {