Converted Observatory refs elements

runtime/observatory/tests/observatory_ui/mocks/objects/context.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.
+
+part of mocks;
+
+class ContextRefMock implements M.ContextRef {
+  final String id;
+  final int length;
+
+  const ContextRefMock({this.id, this.length: 0});
+}
+
+class ContextMock implements M.Context {
+  final String id;
+  final M.ClassRef clazz;
+  final int size;
+  final int length;
+  final M.Context parentContext;
+
+  const ContextMock({this.id, this.clazz, this.size, this.length: 0,
+                     this.parentContext});
+}