vp10: code sign bit before absolute value in non-arithcoded header.
For reading, this makes the operation branchless, although it still requires two shifts. For writing, this makes the operation as fast as writing an unsigned value, branchlessly. This is also how other codecs typically code signed, non-arithcoded bitstream elements. See issue 1039. Change-Id: I6a8182cc88a16842fb431688c38f6b52d7f24ead
Showing with 34 additions and 9 deletions