It's done by mediawiki.js, as it says at the bottom of the file.
Change-Id: I2505cde86ff9d9532fce75f3924f88e898a5f5f6
//
// Only 'text', 'parse', and 'escaped' are supported, and the
// actual escaping for 'escaped' is done by other code (generally
//
// Only 'text', 'parse', and 'escaped' are supported, and the
// actual escaping for 'escaped' is done by other code (generally
+ // through mediawiki.js).
//
// However, note that this default only
// applies to direct calls to jqueryMsg. The default for mediawiki.js itself
//
// However, note that this default only
// applies to direct calls to jqueryMsg. The default for mediawiki.js itself