Move a cast in Buffer.indexOf().
Move a cast in Buffer.indexOf().

This has the happy side-effect of preventing the Lenovo S939 from
behaving incorrectly when executing this method.

The following test exercises the previous code; it fails after
a few iterations on that device:
https://gist.github.com/swankjesse/4396e276e43dbb0e71cc

Unfortunately there's no good way to regression test that we
haven't hit a bug in a specific lousy device.

xubuhang/okio,kilink/okio,palaniyappanBala/okio,kilink/okio,msdgwzhy6/okio,v7lin/okio,chenrui2014/okio,seven332/okio,palaniyappanBala/okio,tejasmanohar/okio,msdgwzhy6/okio,Shedings/okio,square/okio,tempbottle/okio,xubuhang/okio,tejasmanohar/okio,v7lin/okio,tomkdir/okio,sunshinecoast/okio,angcyo/okio,patds/okio,chenrui2014/okio,patds/okio,square/okio,seven332/okio,sunshinecoast/okio,square/okio,angcyo/okio,tomkdir/okio,tempbottle/okio,Shedings/okio