Remove unnecessary coupling between Promise tests and Object.observe

test/mjsunit/es6/debug-promises/reject-uncaught-late.js

Index: test/mjsunit/es6/debug-promises/reject-uncaught-late.js
diff --git a/test/mjsunit/es6/debug-promises/reject-uncaught-late.js b/test/mjsunit/es6/debug-promises/reject-uncaught-late.js
index 4a883da13a793972d00fd2f4a9f8311b15b04811..7e10be901f9bf2925a3814303a67ec8142537706 100644
--- a/test/mjsunit/es6/debug-promises/reject-uncaught-late.js
+++ b/test/mjsunit/es6/debug-promises/reject-uncaught-late.js
@@ -67,10 +67,7 @@ function testDone(iteration) {
     }
   }
 
-  // Run testDone through the Object.observe processing loop.
-  var dummy = {};
-  Object.observe(dummy, checkResult);
-  dummy.dummy = dummy;
+  Promise.resolve().then(checkResult);
 }
 
 testDone(0);