Converted Observatory refs elements

runtime/observatory/lib/src/models/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 models;
+
+abstract class ContextRef extends ObjectRef {
+  /// The number of variables in this context.
+  int get length;
+}
+
+abstract class Context extends Object implements ContextRef {
+  /// [optional] The enclosing context for this context.
+  Context get parentContext;
+
+  // The variables in this context object.
+  //Iterable<ContextElement> get variables;
+}