Converted Observatory context-view element

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});
+  const ContextRefMock({this.id: 'context-id', this.length});
 }
 
 class ContextMock implements M.Context {
   final String id;
   final M.ClassRef clazz;
   final int size;
   final int length;
   final M.Context parentContext;
+  final Iterable<M.ContextElement> variables;
 
-  const ContextMock({this.id, this.clazz, this.size, this.length: 0,
-                     this.parentContext});
+  const ContextMock({this.id: 'context-id', this.clazz: const ClassMock(),
+                     this.size: 0, this.length, this.parentContext,
+                     this.variables: const []});
 }
+
+class ContextElementMock implements M.ContextElement {
+  final GuardedMock<M.InstanceRef> value;
+
+  const ContextElementMock({this.value: const GuardedMock.fromValue(
+      const InstanceRefMock())});
+}