Fix MathJax not rendering in Chrome when sessionStorage is disabled.

[merijn]

If a user has disabled data storage, then accessing "window.sessionStorage" for the typeof throws a SecurityError, stopping MathJax from rendering. The solution is to simply wrap the access to window.sessioStorage in a try/catch and return "undefined" if it throws an exception.

[fred-wang]

I just saw your message on IRC... thanks for your patch! The changes look good to me but I'd like to have Davide's point of view for coding style and so on. @dpvc: can you review that?

[dpvc]

I suspect the whole check for Chrome is no longer needed (this was to get around a bug in Chrome 5 (beta), apparently), so I would guess it is safe to remove the whole thing. I'll have to check to make sure the stylesheets can be detected in current versions of Chrome.

The stylesheet detection was pretty fragile (the second most fragile part of MathJax after font detection), and probably deserves looking at again, now that it is 5 years later and browsers have changed a lot. There are some Safari2 things in there, too, as I recall, that could be removed.

[merijn]

Either would be fine with me, the biggest problem I run into now is that MathJax doesn't render with cookies disabled, as disabling cookies also disables sessionStorage in Chrome.

[pkra]

Could we turn this into an issue instead? (It would also solve the problem of a CLA if this isn't the way to solve the underlying issue...).

[fred-wang]

I'm adding this to the milestone and assigning this to Davide.

[pkra]

Just a reminder: we can't merge this until we sort out a CLA.

[dpvc]

I'm expecting to remove the test entirely, so it will not be a merge (sorry merljn). So I don't think a CLA will be needed.

[fred-wang]

I'm closing this and I opened a normal issue instead: #584