Before the fix, the message tray highlighted all urls containing "://", even
invalid ones. This change fixes this by have the message tray highlight only
the urls with http, https, ftp schemes.
Credit goes to: Phuong Vu, Liye Fu, Monica Chelliah, Owen Taylor
https://bugzilla.gnome.org/show_bug.cgi?id=661225
'(^|' + _leadingJunk + ')' +
'(' +
'(?:' +
- '[a-z][\\w-]+://' + // scheme://
+ '(?:http|https|ftp)://' + // scheme://
'|' +
'www\\d{0,3}[.]' + // www.
'|' +