Push Notification - always set latestUpdateTimestampMs

Service worker will start notifying only about new changes once it
starts. This also simplify current code.

Release-Notes: skip
Change-Id: I8188c3e460aea972761318c5211d1aafec911dc9

polygerrit-ui/app/utils/service-worker-util.ts

diff --git a/polygerrit-ui/app/utils/service-worker-util.ts b/polygerrit-ui/app/utils/service-worker-util.ts
index 3cf0dce..eb547ea 100644
--- a/polygerrit-ui/app/utils/service-worker-util.ts
+++ b/polygerrit-ui/app/utils/service-worker-util.ts
@@ -15,9 +15,8 @@
 export function filterAttentionChangesAfter(
   changes: ParsedChangeInfo[],
   account: AccountDetailInfo,
-  latestUpdateTimestampMs?: number
+  latestUpdateTimestampMs: number
 ) {
-  if (!latestUpdateTimestampMs) return changes;
   return changes.filter(change => {
     const attention_set = change.attention_set![account._account_id!];
     if (!attention_set.last_update) return false;

polygerrit-ui/app/workers/service-worker-class.ts

diff --git a/polygerrit-ui/app/workers/service-worker-class.ts b/polygerrit-ui/app/workers/service-worker-class.ts
index c93dd2f..c469644 100644
--- a/polygerrit-ui/app/workers/service-worker-class.ts
+++ b/polygerrit-ui/app/workers/service-worker-class.ts
@@ -16,7 +16,7 @@
 export class ServiceWorker {
   constructor(private ctx: ServiceWorkerGlobalScope) {}
 
-  latestUpdateTimestampMs?: number;
+  latestUpdateTimestampMs = Date.now();
 
   showNotification(change: ParsedChangeInfo, account: AccountDetailInfo) {
     const body = getReason(undefined, account, change);
@@ -38,12 +38,10 @@
   async getChangesToNotify(account: AccountDetailInfo) {
     // We throttle polling, since there can be many clients triggerring
     // always only one service worker.
-    if (this.latestUpdateTimestampMs) {
-      const durationFromLatestUpdateMS =
-        Date.now() - this.latestUpdateTimestampMs;
-      if (durationFromLatestUpdateMS < TRIGGER_NOTIFICATION_UPDATES_MS) {
-        return [];
-      }
+    const durationFromLatestUpdateMS =
+      Date.now() - this.latestUpdateTimestampMs;
+    if (durationFromLatestUpdateMS < TRIGGER_NOTIFICATION_UPDATES_MS) {
+      return [];
     }
     const prevLatestUpdateTimestampMs = this.latestUpdateTimestampMs;
     this.latestUpdateTimestampMs = Date.now();