Observatory: Report peak process memory usage.

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 91566e917e73dbccc516341e3a9633f6f5ca31d8..fabc340c386f945811bf77dc033e5b073f57d895 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -632,6 +632,7 @@ abstract class VM extends ServiceObjectOwner implements M.VM {
   @observable bool assertsEnabled = false;
   @observable bool typeChecksEnabled = false;
   @observable int pid = 0;
+  @observable int maxRSS = 0;
   @observable bool profileVM = false;
   @observable DateTime startTime;
   @observable DateTime refreshTime;
@@ -909,6 +910,7 @@ abstract class VM extends ServiceObjectOwner implements M.VM {
     refreshTime = new DateTime.now();
     notifyPropertyChange(#upTime, 0, 1);
     pid = map['pid'];
+    maxRSS = map['_maxRSS'];
     profileVM = map['_profilerMode'] == 'VM';
     assertsEnabled = map['_assertsEnabled'];
     typeChecksEnabled = map['_typeChecksEnabled'];