RFR: 8252093: formula used to calculate decaying variance in numberSeq

[Albert Yang]

 > Have you run any benchmarks and compared scores as well as GC-behavior?

Checking SPECjbb2015 now. What kind of GC behavior do you have in mind?

 > Is there a good reason for keeping it inverted

The only thing I can think of is to avoid invasive change. I am more leaned towards 
changing it to be consistent with the literature.

-- 
/Albert