libvpx

Move input frame scaling into the recode loop

Move the point at which input frames are scaled
into the recode loop. This will allow us to change
the coded frame size dynamically in response
to previous attempts to encode the frame at a
higher resolution.

A following patch will implement a scheme for
resizing the frame in the recode loop.

Change-Id: I6a59c02d6ac1626512edad6de8b60063b79433e6