[Background Sync] Show updated delay in Devtools.

We sometimes change the actual delay after which a periodicsync event is fired
based on other registrations for the origin. Update what we show in Devtools so
it corresponds to the actual delay_until set on the registration.

Bug: 989524
Change-Id: I9ba06f9c5f65d93775b0a9bf9d934f1d9b5b5ce6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730921Reviewed-by: Rayan Kanso <rayankans@chromium.org>
Commit-Queue: Mugdha Lakhani <nator@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683298}

content/browser/background_sync/background_sync_manager.cc

@@ -918,7 +918,8 @@ void BackgroundSyncManager::RegisterDidGetDelay(
         DevToolsBackgroundService::kPeriodicBackgroundSync,
         /* event_name= */ "Got next event delay",
         /* instance_id= */ registration.options()->tag,
-        {{"Next Attempt Delay (ms)", GetDelayAsString(delay)}});
+        {{"Next Attempt Delay (ms)",
+          GetDelayAsString(registration.delay_until() - clock_->Now())}});
   }
 
   AddOrUpdateActiveRegistration(
@@ -1980,7 +1981,8 @@ void BackgroundSyncManager::EventCompleteDidGetDelay(
     std::string event_name = GetSyncEventName(registration->sync_type()) +
                              (succeeded ? " event completed" : " event failed");
     std::map<std::string, std::string> event_metadata = {
-        {"Next Attempt Delay (ms)", GetDelayAsString(delay)}};
+        {"Next Attempt Delay (ms)",
+         GetDelayAsString(registration->delay_until() - clock_->Now())}};
     if (!succeeded) {
       event_metadata.emplace("Failure Reason",
                              GetEventStatusString(status_code));