Reland "Move alpha modulation into paint conversion (Step 1)"
This is a reland of c77620c308f9e3c9f8246ef663bb43183336ab75
Original change's description:
> Move alpha modulation into paint conversion (Step 1)
>
> Skia has a rule that says (roughly), any SkShader is modulated by the
> paint alpha. The CPU backend implements this precisely - the entire
> shader sees the opaque paint color, and the alpha is applied once at
> the root. The GPU backend has previously made each SkShader responsible
> for doing this modulation. That led to two kinds of problems:
>
> 1) Some shaders forgot to do the modulation at all.
> 2) In shader trees, it's possible for the alpha to get applied
> multiple times, or to child effects where it isn't desired.
>
> A consequence of #2 is that the GPU implementation of things like
> blend-shaders have to jump through hoops to invoke their children with
> opaque versions of their input colors.
>
> This CL allows us to remove the explicit alpha modulation from a variety
> of shaders, and should also cleanup of the blend shader logic. However,
> to get the CL past chrome's layout tests, we need to guard the change.
> So this version just makes the major change so paint conversion, in a
> way that will work universally. Once chrome switches to the new method,
> it will be safe to clean up the various shader implementations.
>
> Bug: skia:11942
> Change-Id: I518534becdd5d10cbd78cf3ff7d4a46dd1faabf9
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/464116
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
Cq-Do-Not-Cancel-Tryjobs: true
Bug: skia:11942
Change-Id: I3bf184932adbb425959b02d28af1e6b7f5d127d5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/464928
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed