Remove unnecessary coupling between Promise tests and Object.observe

test/mjsunit/es6/debug-promises/reject-with-undefined-reject.js

Index: test/mjsunit/es6/debug-promises/reject-with-undefined-reject.js
diff --git a/test/mjsunit/es6/debug-promises/reject-with-undefined-reject.js b/test/mjsunit/es6/debug-promises/reject-with-undefined-reject.js
index d11c01ff73b6216cab278aa850e7fa45c49cf2d8..bc40d803daed9b7791112b31aa98b855df6ada9d 100644
--- a/test/mjsunit/es6/debug-promises/reject-with-undefined-reject.js
+++ b/test/mjsunit/es6/debug-promises/reject-with-undefined-reject.js
@@ -66,10 +66,7 @@ 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);