frameDate update problem

[bvjustin]

With the change to make the loopTimes variable thread safe, the actual values are now stored in the Atomic values, the didSet no longer gets called because the loopTimes atomic object itself does not get set, it's the atomic object's .values property that gets set. So to fix this, need to remove the didSet method for the variable and instead update the index manually whenever the loopTimes.values is set.