Moved isolate high watermark calculations into the Observatory client.

runtime/observatory/lib/src/service/object.dart

Index: runtime/observatory/lib/src/service/object.dart
diff --git a/runtime/observatory/lib/src/service/object.dart b/runtime/observatory/lib/src/service/object.dart
index ccc9054597b92b533b9fa16d6c53f5a9fdc20d47..f4491284d0f5f8534f42eef4430736814fad295f 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -1645,10 +1645,14 @@ class Isolate extends ServiceObjectOwner implements M.Isolate {
       threads.addAll(map['_threads']);
     }
 
-    _memoryHighWatermark = int.parse(map['_memoryHighWatermark']);
+    int currentMemoryHighWatermark = 0;
+    for (var i = 0; i < threads.length; i++) {
+      currentMemoryHighWatermark += threads[i].memoryHighWatermark;
+    }
 
-    if (map['threads'] != null) {
-      threads.addAll(map['threads']);
+    if (_memoryHighWatermark == null ||

[Cutch, 2017/01/25 21:22:33]

please initialize _memoryHighWatermark to 0 and drop the null check.

[bkonyi, 2017/01/25 21:51:32]

Done.

+        currentMemoryHighWatermark > _memoryHighWatermark) {
+      _memoryHighWatermark = currentMemoryHighWatermark;
     }
 
     _numZoneHandles = map['_numZoneHandles'];