Fix flaky SW registration in PushMessaging/BudgetManager browser tests

chrome/test/data/budget_service/service_worker.js

Index: chrome/test/data/budget_service/service_worker.js
diff --git a/chrome/test/data/budget_service/service_worker.js b/chrome/test/data/budget_service/service_worker.js
index 5ebfb6416e07267edd7132323e872c63baaab7cf..753754022b76b50fc58121c6a27a3ec509e6d1ec 100644
--- a/chrome/test/data/budget_service/service_worker.js
+++ b/chrome/test/data/budget_service/service_worker.js
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Don't wait for clients of old SW to close before activating.
+self.addEventListener('install', () => skipWaiting());
+
 // Accept messages from the test JavaScript to trigger worker based tests.
 self.addEventListener('message', function (event) {
   if (event.data.command == 'workerGet') {