Add map transition for observed objects

src/object-observe.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 198 matching lines @@
     throw MakeTypeError("observe_accept_invalid");
 
   if (!observerInfoMap.has(callback)) {
     observerInfoMap.set(callback, {
       pendingChangeRecords: null,
       priority: observationState.observerPriority++,
     });
   }
 
   var objectInfo = objectInfoMap.get(object);
-  if (IS_UNDEFINED(objectInfo)) objectInfo = CreateObjectInfo(object);
-  %SetIsObserved(object, true);
+  if (IS_UNDEFINED(objectInfo)) {
+    objectInfo = CreateObjectInfo(object);
+    %SetIsObserved(object);
+  }
 
   EnsureObserverRemoved(objectInfo, callback);
 
   var observer = CreateObserver(callback, accept);
   if (ObserverIsActive(observer, objectInfo))
     objectInfo.changeObservers.push(observer);
   else
     objectInfo.inactiveObservers.push(observer);
 
   return object;
 }
 
 function ObjectUnobserve(object, callback) {
   if (!IS_SPEC_OBJECT(object))
     throw MakeTypeError("observe_non_object", ["unobserve"]);
   if (!IS_SPEC_FUNCTION(callback))
     throw MakeTypeError("observe_non_function", ["unobserve"]);
 
   var objectInfo = objectInfoMap.get(object);
   if (IS_UNDEFINED(objectInfo))
     return object;
 
   EnsureObserverRemoved(objectInfo, callback);
-
-  if (objectInfo.changeObservers.length === 0 &&
-      objectInfo.inactiveObservers.length === 0) {
-    %SetIsObserved(object, false);
-  }
-
   return object;
 }
 
 function ArrayObserve(object, callback) {
   return ObjectObserve(object, callback, ['new',
                                           'updated',
                                           'deleted',
                                           'splice']);
 }
 
@@ skipping 186 matching lines @@
     "observe", ArrayObserve,
     "unobserve", ArrayUnobserve
   ));
   InstallFunctions(notifierPrototype, DONT_ENUM, $Array(
     "notify", ObjectNotifierNotify,
     "performChange", ObjectNotifierPerformChange
   ));
 }
 
 SetupObjectObserve();