We were hoping to get away with a single double density sprite, but alas, as you point out, not all devices support background-size. Not just old Android, but also old Blackberry (pre webkit), and Opera Mini.
We feature detect background-size in the head of the page and add a class name to the html element. We need to browser sniff opera mini as it gives a false positive on the test.
We only offline cache the larger sprite, assuming browsers that support appcache also support background-size.
We feature detect background-size in the head of the page and add a class name to the html element. We need to browser sniff opera mini as it gives a false positive on the test.
We only offline cache the larger sprite, assuming browsers that support appcache also support background-size.