Enable dual arf with constant q.

Add second level arf Q adjustment when using dual arfs
in constant Q mode.

Previously in constant Q mode enabling dual arf hurt by ~5%
but with this change the average benefit is ~1-1.5% with some
mid range data points up ~10%.

Note however that it still hurts on some clips including
some very low motion show content.

Change-Id: I5b7789a2f42a6127d9e801cc010c20a7113bdd9b
Move frame re-sizing into the recode loop

The point at which frames are scaled to their
coded dimensions is moved into the re-code loop.

This is in preparation for a further patch that
will add logic into the re-code loop to reduce
the coded frame size if the encoder is struggling
to hit the target data rate at the native frame
size.

Change-Id: Ie4131f5ec6fb93148879f6ce96123296442bf2d1
Merge "Move frame re-sizing into the recode loop"
Merge "Enable dual arf with constant q."