The nominal tx_type for a given mode is used as a context
to encode the actual tx_type for intra.
Results:
derflr: -0.241% BDRATE
hevcmr: -0.366% BDRATE
Change-Id: Icfe7b0a58d79bc6497a06e3441779afec6e01e21
Add palette mode for keyframe luma channel. Palette mode is enabled
when using "--tune-content=screen" in encoding config parameters.
on screen_content testset: +6.89%
on derlr : +0.00%
Design doc (WIP):
https://goo.gl/lD4yJw
Change-Id: Ib368b216bfd3ea21c6c27436934ad87afdaa6f88
