Since it has been 4 years that this request has been in, I think it needs some sort of follow-up.
The webvpn/Anyconnect functionality from either an ASA or an ISR doesn't work due to the reliance on java, and specifically on the java plugins on the client side.
The web page login/vpn initiation ONLY works with Windows and Internet explorer or Edge with Active X. Even then, there is client browser configuration that needs to happen before this works.
No other O/S/Browser combo works. Macs, Linux, Firefox, Chrome, etc. etc.
If there is something coming out that will replace Anyconnect and drop java, I would like to hear about it!
Otherwise, Cisco - Please fix this!
Edit: Of course, the other avenue is to get Oracle to fix the java plugin...