Implement color filter as GrGLEffect

src/gpu/gl/GrGLProgramDesc.cpp

Index: src/gpu/gl/GrGLProgramDesc.cpp
diff --git a/src/gpu/gl/GrGLProgramDesc.cpp b/src/gpu/gl/GrGLProgramDesc.cpp
index 8b731fbc2c71244e80a6f6dc87262280e31e214a..b53fa89fe9ccd2639e50e9c8f045c7beecf2b612 100644
--- a/src/gpu/gl/GrGLProgramDesc.cpp
+++ b/src/gpu/gl/GrGLProgramDesc.cpp
@@ -70,7 +70,8 @@ void GrGLProgramDesc::Build(const GrDrawState& drawState,
 
     bool colorIsTransBlack = SkToBool(blendOpts & GrDrawState::kEmitTransBlack_BlendOptFlag);
     bool colorIsSolidWhite = (blendOpts & GrDrawState::kEmitCoverage_BlendOptFlag) ||
-                             (!requiresColorAttrib && 0xffffffff == drawState.getColor());
+                             (!requiresColorAttrib && 0xffffffff == drawState.getColor()) ||
+                             (drawState.numColorStages() > 0 && !(*drawState.getColorStage(0).getEffect())->willUseInputColor());
 
     int numEffects = (skipColor ? 0 : drawState.numColorStages()) +
                      (skipCoverage ? 0 : drawState.numCoverageStages());
@@ -111,7 +112,6 @@ void GrGLProgramDesc::Build(const GrDrawState& drawState,
 
     header->fHasVertexCode = hasVertexCode || requiresLocalCoordAttrib;
     header->fEmitsPointSize = isPoints;
-    header->fColorFilterXfermode = skipColor ? SkXfermode::kDst_Mode : drawState.getColorFilterMode();
 
     // Currently the experimental GS will only work with triangle prims (and it doesn't do anything
     // other than pass through values from the VS to the FS anyway).
@@ -200,11 +200,6 @@ void GrGLProgramDesc::Build(const GrDrawState& drawState,
     bool separateCoverageFromColor = false;
     if (!drawState.isCoverageDrawing() && !skipCoverage &&
         (drawState.numCoverageStages() > 0 || requiresCoverageAttrib)) {
-        // color filter is applied between color/coverage computation
-        if (SkXfermode::kDst_Mode != header->fColorFilterXfermode) {
-            separateCoverageFromColor = true;
-        }
-
         // If we're stenciling then we want to discard samples that have zero coverage
         if (drawState.getStencil().doesWrite()) {
             header->fDiscardIfZeroCoverage = true;