db228913e4
`notificationBox.appendNotification` is now async, so in cases where we were receiving multiple "cdm-not-installed" messages in quick succession it was possible that the notification from the prior call hadn't actully been appended yet. This made it so that calls to `notificationBox.getNotificationWithValue` wouldn't return anything, and we would show the same message multiple times. This patch adds code to track which notification related messages are being handled to avoid re-appending the same notification. Differential Revision: https://phabricator.services.mozilla.com/D200030