Revert of Implement Porter Duff XP with a blend table (patchset #12 id:220001 of https://codereview.chromium.org/1124373002/)

Reason for revert:
Blocking DEPS roll into Chromium. Crashing virtual/gpu/fast/canvas/canvas-composite-*.html tests with the assert

../../third_party/skia/src/gpu/gl/builders/GrGLFragmentShaderBuilder.cpp:281: failed assertion "k110_GrGLSLGeneration != gpu->glslGeneration() || fOutputs.empty()"

Original issue's description:
> Implement Porter Duff XP with a blend table
>
> Removes the runtime logic used by PorterDuffXferProcessor to decide
> blend coeffs and shader outputs, and instead uses a compile-time
> constant table of pre-selected blend formulas.
>
> Introduces a new blend strategy for srcCoeff=0 that can apply coverage
> with a reverse subtract blend equation instead of dual source
> blending.
>
> Adds new macros in GrBlend.h to analyze blend formulas both runtime.
>
> Removes kSetCoverageDrawing_OptFlag and GrSimplifyBlend as they are no
> longer used.
>
> Adds a GM that verifies all xfermodes, including arithmetic, with the
> color/coverage invariants used by Porter Duff.
>
> Adds a unit test that verifies each Porter Duff formula with every
> color/coverage invariant.
>
> Major changes:
>
>  * Uses a reverse subtract blend equation for coverage when srcCoeff=0
>    (clear, dst-out [Sa=1], dst-in, modulate). Platforms that don't
>    support dual source blending no longer require a dst copy for
>    dst-in and modulate.
>
>  * Sets BlendInfo::fWriteColor to false when the blend does not modify
>    the dst. GrGLGpu will now use glColorMask instead of blending for
>    these modes (dst, dst-in [Sa=1], modulate ignored for [Sc=1]).
>
>  * Converts all SA blend coeffs to One for opaque inputs, and ISA to
>    Zero if there is also no coverage. (We keep ISA around when there
>    is coverage because we use it to tweak alpha for coverage.)
>
>  * Abandons solid white optimizations for the sake of simplicity
>    (screen was the only mode that previous had solid white opts).
>
> Minor differences:
>
>  * Inconsequential differences in opt flags (e.g. we now return
>    kCanTweakAlphaForCoverage_OptFlag even when there is no coverage).
>
>  * Src coeffs when the shader outputs 0.
>
>  * IS2C vs IS2A when the secondary output is scalar.
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/9a70920db22b6309c671f8e5d519bb95570e4414

TBR=egdaniel@google.com,bsalomon@google.com,cdalton@nvidia.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1153993002

1 files changed, 8 insertions, 0 deletions

diff --git a/include/gpu/GrXferProcessor.h b/include/gpu/GrXferProcessor.h
index 85e5aa04ed..8458a620fe 100644
--- a/include/gpu/GrXferProcessor.h
+++ b/include/gpu/GrXferProcessor.h
@@ -51,6 +51,10 @@ enum GrBlendEquation {
 
 static const int kGrBlendEquationCnt = kLast_GrBlendEquation + 1;
 
+inline bool GrBlendEquationIsAdvanced(GrBlendEquation equation) {
+    return equation >= kFirstAdvancedGrBlendEquation;
+}
+
 /**
  * Coeffecients for alpha-blending.
  */
@@ -139,6 +143,10 @@ public:
          */
         kOverrideColor_OptFlag            = 0x8,
         /**
+         * Set CoverageDrawing_StateBit
+         */
+        kSetCoverageDrawing_OptFlag       = 0x10,
+        /**
          * Can tweak alpha for coverage. Currently this flag should only be used by a batch
          */
         kCanTweakAlphaForCoverage_OptFlag = 0x20,