Converted Observatory persistent-hangles-page element

runtime/observatory/lib/src/models/objects/persistent_handles.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 PersistentHandles {
+  Iterable<PersistentHandle> get elements;
+  Iterable<WeakPersistentHandle> get weakElements;
+}
+
+abstract class PersistentHandle {
+  ObjectRef get object;
+}
+
+abstract class WeakPersistentHandle implements PersistentHandle {
+  int get externalSize;
+  String get peer;
+  String get callbackSymbolName;
+  String get callbackAddress;
+}