web_app: fix flaky badging browsertest

Fix WebAppBadgingBrowserTest to wait for service workers to be
active before testing sending messages to sub app service worker.

Bug: 1085547
Change-Id: Ie24b192b4d2f5654f300d935e11a50637df52ea4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2213021
Commit-Queue: Phillis Tang <phillis@chromium.org>
Reviewed-by: Chase Phillips <cmp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771706}

chrome/test/data/web_app_badging/badging_with_frames_and_workers.html

@@ -14,6 +14,24 @@
     const crossSiteUrl = new URLSearchParams(location.search).get('url');
     crossFrame.src = crossSiteUrl;
 
+    // Copy of //content/test/data/service_worker/create_service_worker.html.
+
+    // Simulates navigator.serviceWorker.ready, which can't be used since this
+    // document may not be in-scope.
+    async function whenReady(registration) {
+      if (registration.active)
+        return;
+      // If there's no .active, .waiting will activate before .installing.
+      const nextActiveWorker = registration.waiting || registration.installing;
+      return new Promise((resolve, reject) => {
+        nextActiveWorker.addEventListener('statechange', event => {
+          if (nextActiveWorker.state == 'activated')
+            resolve();
+          if (nextActiveWorker.state == 'redundant')
+            reject('worker became redundant');
+        });
+      });
+    }
     // BrowserTests should use EvalJs() to call registerServiceWorker().
     // EvalJs() provides this function's return value, which enables the
     // BrowserTest to verify successful service worker registration.
@@ -22,7 +40,13 @@
     //               "registerServiceWorker(script, scope);"));
     async function registerServiceWorker(script, scope) {
       try {
-        await navigator.serviceWorker.register(script, { scope });
+        const init = scope ? {scope} : {};
+        const registration =
+            await navigator.serviceWorker.register(script, init);
+        // wait for serviceworker to be active, otherwise
+        // navigator.serviceWorker.getRegistration might get serviceworker of
+        // parent scope
+        await whenReady(registration);
         return 'OK';
       } catch (error) {
         return `EXCEPTION: ${error}`;