add bitmap shaders to P3

Update SkImageShader/SkBlitter_sprite to use SkPaint::getColor4f().

Split the set_rgb into bounded and unbounded variants, just like we did
with uniform_color (the exact rgba variant).  Without this we'd try to
draw out-of-gamut colors in lowp for the non-scaled shader draw in
--config srgb, and that can't work.  SkRasterPipeline::append_set_rgb()
now checks to see if it's safe to use ::set_rgb and lowp, falling back
on ::unbounded_set_rgb and floats.

In the GM, the new "sprite" case is handled by SkImageShader, and the
old "sprite" case is handled as a uniform color draw through an A8 mask.
I'm having trouble constructing a call that reaches the A8 code in
SkBlitter_Sprite, but I have confirmed that it's definitely used by
quickly running the other GMs.  I've updated it to use the float paint
color just like SkImageShader.

Change-Id: I1ca8c08b79631165ac0c0032a1406add80e55c9f
Reviewed-on: https://skia-review.googlesource.com/154624
Auto-Submit: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
6 files changed