Remove unnecessary coupling between Promise tests and Object.observe

test/mjsunit/es6/debug-promises/throw-uncaught-uncaught.js

Index: test/mjsunit/es6/debug-promises/throw-uncaught-uncaught.js
diff --git a/test/mjsunit/es6/debug-promises/throw-uncaught-uncaught.js b/test/mjsunit/es6/debug-promises/throw-uncaught-uncaught.js
index 69aa8ebbd248c2e6fd01770aca7b47126526ce53..faa8629692a7e36e139f0b8be8f46e905bcf02dc 100644
--- a/test/mjsunit/es6/debug-promises/throw-uncaught-uncaught.js
+++ b/test/mjsunit/es6/debug-promises/throw-uncaught-uncaught.js
@@ -61,10 +61,7 @@ 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);