use partitioning from last frame

use partitioning from last frame

This cl converts use partition from last frame to do the following:

if part is none,horz, vert -> try split
if part != none and one of the children is not split - try none

Change-Id: I5b6c659e35f3ac9f11c051b92ba98af6d7e8aa87
Signed-off-by: Jim Bankoski <jimbankoski@google.com>