Added ability to request zone memory information for all isolates through the VM service and added …

runtime/observatory/lib/src/models/objects/zone.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 Zone {
+  /// The total amount of memory allocated in the zone, including
+  /// memory that is not actually being used.
+  num get capacity;

[Cutch, 2016/12/16 22:55:43]

int here and below

[bkonyi, 2016/12/16 22:59:57]

Done.

+
+  /// The total amount of memory actually used in the zone.
+  num get used;
+}