Remove Chrome bug workaround

Fixed in Google Chrome version 39

Conflicts:
	client/options.js
Chache blurred background

Conflicts:
	client/options.js
Improve gar and mawaru theme responsiveness

* Significantly increases responsoveness with the gar and mawaru theme in large threads
* Avoids Firefox bug https://bugzilla.mozilla.org/show_bug.cgi?id=671302