L2E: let external rate control pass in a max frame size

And allow the frame to recode when the frame size is larger
than the input max frame size.

If the max frame size is not specified, let vp9 decide whether
to recode.  The recode follows the vp9's current recoding mechanism.

The rate control api will return the new qindex back to the
external model.

Change-Id: I796fbf713ad50a5b413b0e2501583b565ed2343f
5 files changed