vp9-realtime: Move frame dropper to after scene detection.

Move frame dropper to after scene detection and noise estimation.
Scene detection and noise estimation operate on source data and
update metrics along sequence, so they should be moved before
the frame dropper.

Also we don't want to drop on scene change, as the scene detection
and (possible) re-encode step will be missed.

Change-Id: I3d9e16d785bd5ace6707db2abce77ddc110bfef4
2 files changed