non-linear blending first steps

Code:
  - Add a non-linear blending bit and makeNonlinearBlending()
    to SkColorSpace
  - remove enough F16=linear checks to make it possible to
    create surfaces and encode pngs with nonlinear F16

Testing:
  - add "esrgb" software config to DM, run it
  - add "srgbnl" software config, run it
  - deemphasize importance of "srgb" config on bots
  - update unit tests to reflect relaxed F16 constraints
  - add a new unit test file with _really_ basic tests,
    and a new unit test that's not working yet

Bug: skia:7942

Change-Id: I8ac042bdf9f3d791765393b68fd9256375184d83
Reviewed-on: https://skia-review.googlesource.com/127325
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

0 files changed, 0 insertions, 0 deletions