public function listMsgs( $domain ) {
		$domain = $this->normalizeDomain( $domain );
		$this->ensureLoaded( $domain, 'en' );
		// Ignore load failure to allow listing of messages that
		// were manually registered (in case there are any).
		if ( !isset( $this->messageBlob[$domain]['en'] ) ) {
			return [];
		}
		return array_keys( $this->messageBlob[$domain]['en'] );
	}