www/firefox: enable BUNDLED_CAIRO per r393805

Electrolysis is going to require OMTC which had stability issues with
system Cairo. To avoid trainwreck let's get more exposure.

https://wiki.mozilla.org/Electrolysis#Schedule

PR:		202174 (ping)

www/firefox/Makefile

@@ -4,6 +4,7 @@
 PORTNAME=	firefox
 DISTVERSION=	43.0.4
 DISTVERSIONSUFFIX=.source
+PORTREVISION=	1
 PORTEPOCH=	1
 CATEGORIES=	www ipv6
 MASTER_SITES=	MOZILLA/${PORTNAME}/releases/${DISTVERSION}/source \
@@ -49,7 +50,7 @@ MOZ_OPTIONS=	--program-transform-name='s/firefox/${MOZILLA}/' \
 		--enable-official-branding
 
 OPTIONS_EXCLUDE=	GSTREAMER LOGGING
-OPTIONS_DEFAULT=	GTK2
+OPTIONS_DEFAULT=	BUNDLED_CAIRO GTK2
 
 OPTIONS_SINGLE+=	TOOLKIT
 OPTIONS_SINGLE_TOOLKIT=	GTK2 GTK3