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

runtime/observatory/lib/src/models/objects/zone.dart

Index: runtime/observatory/lib/src/models/objects/zone.dart
diff --git a/runtime/observatory/lib/src/models/objects/zone.dart b/runtime/observatory/lib/src/models/objects/zone.dart
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+// 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 in bytes allocated in the zone, including
+  /// memory that is not actually being used.
+  int get capacity;
+
+  /// The total amount of memory in bytes actually used in the zone.
+  int get used;
+}