Atomics: simplify harness/atomicsHelper.js: waitUntil

harness/atomicsHelper.js

@@ -36,10 +36,10 @@ function getReport() {
  * @param {Number} expected The number of agents that are expected to report as active.
  */
 function waitUntil(i32a, index, expected) {
-  while (Atomics.load(i32a, index) !== expected) {
+  let agents = 0;
+  while ((agents = Atomics.load(i32a, index)) !== expected) {
     /* nothing */
   }
-  const agents = Atomics.load(i32a, index);
   assert.sameValue(agents, expected, `'agents' equals the value of 'expected' (${expected})`);
 }