There was a recent update to Lync Server 2013 (including Lync Server 2013 as found in Office 365) that included a new error page for Chrome users.
It appears that Google dropped support for some older APIs that have been deprecated in Chrome. The APIs were for QuickDraw and Carbon.
While I have not had the experience of seeing the error page, I have heard that is reads:
Lync Web App
Google Chrome no longer supports Lync Web App
To join the meeting:
1. Copy the meeting URL
2. Open Internet Explorer or Firefox
3. Past the URL in address bar, and hit Enter
UPDATE (Dec 15, 2014): Microsoft posted something on this issue last night.
And another UPDATE today (Dec 17, 2014): http://support2.microsoft.com/kb/3025563