Don't attempt to transition JSProxy to an observed map / Object.getNotifier() must SetObserved

src/object-observe.js

Index: src/object-observe.js
diff --git a/src/object-observe.js b/src/object-observe.js
index a5c12bf0098b41abffa5101b0e20e8ccec52b241..f5e0d9d563a08e0507d01b03cc519370e49d0215 100644
--- a/src/object-observe.js
+++ b/src/object-observe.js
@@ -394,7 +394,10 @@ function ObjectGetNotifier(object) {
   if (ObjectIsFrozen(object)) return null;
 
   var objectInfo = objectInfoMap.get(object);
-  if (IS_UNDEFINED(objectInfo)) objectInfo = CreateObjectInfo(object);
+  if (IS_UNDEFINED(objectInfo)) {
+    objectInfo = CreateObjectInfo(object);
+    %SetIsObserved(object);
+  }
 
   if (IS_NULL(objectInfo.notifier)) {
     objectInfo.notifier = { __proto__: notifierPrototype };