Sync: don't delay startup except during browser startup

Followup to https://crrev.com/c/1975726

Sync supports delaying the engine startup by 10 seconds. This is meant
for avoiding contention during browser startup.
Before this CL, the 10-second delay would also apply in a few other
(rare) situations, for no particular reason.
After this CL, the delay happens only during browser startup.
This is mostly for simplicity/consistency; it's not expected to have
any real impact.

Bug: 1035874
Change-Id: Icd7ef6989c4cc252913d9060c6e14191d0b7c24f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1989533
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#729712}

components/sync/driver/profile_sync_service.cc

@@ -1061,7 +1061,7 @@ void ProfileSyncService::OnActionableError(const SyncProtocolError& error) {
       // (but not all). Care must be taken however for scenarios like custom
       // passphrase being set.
       sync_prefs_.ClearDirectoryConsistencyPreferences();
-      startup_controller_->TryStart(IsSetupInProgress());
+      startup_controller_->TryStart(/*force_immediate=*/true);
       break;
     case UNKNOWN_ACTION:
       NOTREACHED();
@@ -1299,7 +1299,7 @@ void ProfileSyncService::SyncAllowedByPlatformChanged(bool allowed) {
     // TODO(crbug.com/856179): Evaluate whether we can get away without a full
     // restart (i.e. just reconfigure plus whatever cleanup is necessary). See
     // also similar comment in OnSyncRequestedPrefChange().
-    startup_controller_->TryStart(/*force_immediate=*/false);
+    startup_controller_->TryStart(/*force_immediate=*/true);
   }
 }
 
@@ -1538,7 +1538,7 @@ void ProfileSyncService::OnSyncManagedPrefChange(bool is_sync_managed) {
   } else {
     // Sync is no longer disabled by policy. Try starting it up if appropriate.
     DCHECK(!engine_);
-    startup_controller_->TryStart(IsSetupInProgress());
+    startup_controller_->TryStart(/*force_immediate=*/true);
   }
 }
 
@@ -1575,6 +1575,11 @@ void ProfileSyncService::OnSyncRequestedPrefChange(bool is_sync_requested) {
     // restart (i.e. just reconfigure plus whatever cleanup is necessary).
     // Especially in the CLEAR_DATA case, StopImpl does a lot of cleanup that
     // might still be required.
+    // TODO(crbug.com/1035874): There's no real need to delay the startup here,
+    // i.e. it should be fine to set force_immediate to true. However currently
+    // some tests depend on the startup *not* happening immediately (because
+    // they want to check that Sync (the feature) got disabled, which is hard to
+    // do if the engine starts up again immediately).
     startup_controller_->TryStart(/*force_immediate=*/false);
   }
 }