Added methods to surface number of zone and scoped handles for each isolate.

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

Index: runtime/observatory/lib/src/models/objects/isolate.dart
diff --git a/runtime/observatory/lib/src/models/objects/isolate.dart b/runtime/observatory/lib/src/models/objects/isolate.dart
index 8cc5c79595548bc8abda9071b39484360cf08eb0..02d436d9a8d200123b5f8f8c7534cd203c4b00bf 100644
--- a/runtime/observatory/lib/src/models/objects/isolate.dart
+++ b/runtime/observatory/lib/src/models/objects/isolate.dart
@@ -54,6 +54,12 @@ abstract class Isolate extends IsolateRef {
   /// The list of threads associated with this isolate.
   Iterable<Thread> get threads;
 
+  /// The number of zone handles currently held by this isolate.
+  int get numZoneHandles;
+
+  /// The number of scoped handles currently held by this isolate.
+  int get numScopedHandles;
+
   /// The current pause on exception mode for this isolate.
   //ExceptionPauseMode get exceptionPauseMode;