I can block notification in chrome by set 'off' in notification settings.
And after that when I send notification with chrome.notifications.create I didn't receive any error.
I tried to check permission with chrome.notifications.getPermissionLevel and got 'granted'.
I tried to check that no one notification is appeared with chrome.notifications.getAll, but suddenly they were added, but didn't show.
There is a way to check that I can show a notification to the user?