Remove unnecessary coupling between Promise tests and Object.observe

test/promises-aplus/lib/global.js

Index: test/promises-aplus/lib/global.js
diff --git a/test/promises-aplus/lib/global.js b/test/promises-aplus/lib/global.js
index 1466d2063b5be2351b49a021578cd1091992fbee..e088fe38f31a9dcac0fadbbaaeb71ae634e5130b 100644
--- a/test/promises-aplus/lib/global.js
+++ b/test/promises-aplus/lib/global.js
@@ -34,12 +34,7 @@ var timers = {};
 var currentId = 0;
 
 function PostMicrotask(fn) {
-  var o = {};
-  Object.observe(o, function() {
-    fn();
-  });
-  // Change something to enqueue a microtask.
-  o.x = 'hello';
+  Promise.resolve().then(fn);
 }
 
 setInterval = function(fn, delay) {