Remove unnecessary coupling between Promise tests and Object.observe

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

Index: test/mjsunit/es6/debug-promises/reject-with-invalid-reject.js
diff --git a/test/mjsunit/es6/debug-promises/reject-with-invalid-reject.js b/test/mjsunit/es6/debug-promises/reject-with-invalid-reject.js
index fc6233da8d15e99a72de26147251df207289200b..1d2a8fe61110a7314d92c7f8e0808a96287e78fc 100644
--- a/test/mjsunit/es6/debug-promises/reject-with-invalid-reject.js
+++ b/test/mjsunit/es6/debug-promises/reject-with-invalid-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);