Update 12/17/14 - Added link to KB article.
After applying the Lync Server 2013 December 2014 Cumulative Update, if a user using Google Chrome tries to use the Lync Web App to join a Lync meeting, they will get the following message:
Google Chrome no longer supports Lync Web App
They will need to use Internet Explorer or Firefox if they would like to join the Lync meeting using Lync Web App. Additional information can be found here.