Ensure that Service Worker clients are always returned in MRU order (2)

LayoutTests/http/tests/serviceworker/resources/test-helpers.js

Index: LayoutTests/http/tests/serviceworker/resources/test-helpers.js
diff --git a/LayoutTests/http/tests/serviceworker/resources/test-helpers.js b/LayoutTests/http/tests/serviceworker/resources/test-helpers.js
index 2a8e7122565b9f9b7ed39d424b7d3f284bc56c5f..9c74737a70e92a4fc26007029e3212140c621eb7 100644
--- a/LayoutTests/http/tests/serviceworker/resources/test-helpers.js
+++ b/LayoutTests/http/tests/serviceworker/resources/test-helpers.js
@@ -65,6 +65,23 @@ function with_sandboxed_iframe(url, sandbox) {
     });
 }
 
+// Creates a new popup window, returning a Promise that resolves to its global
+// scope.
+var with_popup = function(url) {
+  return new Promise(function(resolve, reject) {
+    var win = window.open(url);
+    var interval = setInterval(function() {
+      if (win.location.href.startsWith("http")) {
+        clearInterval(interval);
+        setTimeout(function() {
+          resolve(win);
+        }, 10);
+      }
+    }, 20);
+  });
+}
+
+
 function normalizeURL(url) {
   return new URL(url, self.location).toString().replace(/#.*$/, '');
 }