Remember when an isolate was paused and subtly display it in Obseravatory

runtime/vm/service/service.md

Index: runtime/vm/service/service.md
diff --git a/runtime/vm/service/service.md b/runtime/vm/service/service.md
index 17f46a83688be6b23582e1139d22bbebe42c1a8c..3b24aee6000f3918a44cb00b76a8550134e2c865 100644
--- a/runtime/vm/service/service.md
+++ b/runtime/vm/service/service.md
@@ -959,6 +959,11 @@ class Event extends Response {
   // The isolate with which this event is associated.
   @Isolate isolate;
 
+  // The timestamp (in milliseconds since the epoch) associated with this event.
+  // For some isolate pause events, the timestamp is from when the isolate was
+  // paused. For other events, the timestamp is from when the event was created.
+  int timestamp;
+
   // The breakpoint which was added, removed, or resolved.
   //
   // This is provided for the event kinds: