Previousy, all strings from all JS files were translated in the default
'civicrm' domain, and they were transmitted via CRM.strings.

Now, strings from extension JS files are translated in their respective
domains, and they are transmitted via CRM['strings::'+domain].  If a string
is unavailable in the extension's domain, then it is translated using the
default 'civicrm' domain.

Strings from core JS files are still processed as before.