[flutter_tools] automatically update to latest sw on install (#65784)

If a new service worker is installed, automatically update this behind the scenes. Immediately after a page refresh, the new worker and cache will be available, though the main.dart.js and others will be available sooner due to the cache busting URLS

packages/flutter_tools/lib/src/build_system/targets/web.dart

diff --git a/packages/flutter_tools/lib/src/build_system/targets/web.dart b/packages/flutter_tools/lib/src/build_system/targets/web.dart
index 773eb80..cdf866b 100644
--- a/packages/flutter_tools/lib/src/build_system/targets/web.dart
+++ b/packages/flutter_tools/lib/src/build_system/targets/web.dart
@@ -476,6 +476,7 @@
   ${coreBundle.map((String file) => '"$file"').join(',\n')}];
 // During install, the TEMP cache is populated with the application shell files.
 self.addEventListener("install", (event) => {
+  skipWaiting();
   return event.waitUntil(
     caches.open(TEMP).then((cache) => {
       return cache.addAll(
@@ -579,10 +580,12 @@
   // SkipWaiting can be used to immediately activate a waiting service worker.
   // This will also require a page refresh triggered by the main worker.
   if (event.data === 'skipWaiting') {
-    return self.skipWaiting();
+    skipWaiting();
+    return;
   }
-  if (event.message === 'downloadOffline') {
+  if (event.data === 'downloadOffline') {
     downloadOffline();
+    return;
   }
 });
 
@@ -628,5 +631,11 @@
     })
   );
 }
+
+function skipWaiting() {
+  if (self.skipWaiting != undefined) {
+    self.skipWaiting();
+  }
+}
 ''';
 }