Remove unnecessary coupling between Promise tests and Object.observe

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

Index: test/mjsunit/es6/debug-promises/throw-uncaught-all.js
diff --git a/test/mjsunit/es6/debug-promises/throw-uncaught-all.js b/test/mjsunit/es6/debug-promises/throw-uncaught-all.js
index 72f800bf5b3017b66a52f879260845448c1dd59a..c4bc6c44e3547909b385b0468360dd473c017604 100644
--- a/test/mjsunit/es6/debug-promises/throw-uncaught-all.js
+++ b/test/mjsunit/es6/debug-promises/throw-uncaught-all.js
@@ -61,10 +61,7 @@ function testDone(iteration) {
     }
   }
 
-  // Rerun testDone through the Object.observe processing loop.
-  var dummy = {};
-  Object.observe(dummy, checkResult);
-  dummy.dummy = dummy;
+  %EnqueueMicrotask(checkResult);
 }
 
 testDone(0);