Avoids duplicate computation of UV predictor.

Bit-exact when static_threshold is zero.
Small/neutral difference on RTC set with nonzero static_threshold
(since UV predictor won't be skipped with this change).

Small speed gain, ~1-2%, at speed 8.

Change-Id: Iba8d22a307768b391e29d63c9826aac5a4d9c285