Reimplemented zone memory tracking to avoid race conditions that were causing crashes in the previo…

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 8c1e3672390d3024b7d34140b5f67911f6464c20..f1d1147f8c5917f6d1433ed6555605014d6731ad 100644
--- a/runtime/observatory/lib/src/models/objects/isolate.dart
+++ b/runtime/observatory/lib/src/models/objects/isolate.dart
@@ -54,10 +54,10 @@ abstract class Isolate extends IsolateRef {
   /// The list of threads associated with this isolate.
   Iterable<Thread> get threads;
 
-  /// The maximum amount of memory in bytes allocated by the isolate in all
-  /// threads at a given time. Calculated using the high watermarks of each
+  /// The maximum amount of zone memory in bytes allocated by the isolate in
+  /// all threads at a given time. Calculated using the high watermarks of each
   /// thread alive when a thread is unscheduled.
-  int get memoryHighWatermark;
+  int get zoneHighWatermark;
 
   /// The number of zone handles currently held by this isolate.
   int get numZoneHandles;