To render raw chat mentions in notification text, text-message-spec.js required changes to both messageTitle and notificationTexts. In the first case, markdownRules are passed as a parameter, and in previous diffs, I've added chatMentionCandidates to be used wherever we obtain markdownRules, so chat mentions will be rendered in the parser function. The second case is easier since we operate on a string; the string replace method is used to render chat mentions.

The diff title here should probably include the word "notification" somewhere :)