Rollback trunk to 3.21.15.

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 266 matching lines @@
 
 function AcceptArgIsValid(arg) {
   if (IS_UNDEFINED(arg))
     return true;
 
   if (!IS_SPEC_OBJECT(arg) ||
       !IS_NUMBER(arg.length) ||
       arg.length < 0)
     return false;
 
+  var length = arg.length;
+  for (var i = 0; i < length; i++) {
+    if (!IS_STRING(arg[i]))
+      return false;
+  }
   return true;
 }
 
 // CallbackInfo's optimized state is just a number which represents its global
 // priority. When a change record must be enqueued for the callback, it
 // normalizes. When delivery clears any pending change records, it re-optimizes.
 function CallbackInfoGet(callback) {
   return callbackInfoMap.get(callback);
 }
 
@@ skipping 262 matching lines @@
     "observe", ArrayObserve,
     "unobserve", ArrayUnobserve
   ));
   InstallFunctions(notifierPrototype, DONT_ENUM, $Array(
     "notify", ObjectNotifierNotify,
     "performChange", ObjectNotifierPerformChange
   ));
 }
 
 SetupObjectObserve();