Add support for opaque, unpremul, and premul (both kinds)

Removed 101010x - that's just (1010102, Opaque).
Still needs testing of premul modes.

Bug: skia:
Change-Id: Ie92e968be050180165f57ce57d2c7bf22ea47027
Reviewed-on: https://skia-review.googlesource.com/112565
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
5 files changed