Determine whether we can tweakAlphaForCoverage during Pipeline/XP creation.

src/gpu/effects/GrPorterDuffXferProcessor.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "effects/GrPorterDuffXferProcessor.h"
 
 #include "GrBlend.h"
@@ skipping 312 matching lines @@
                 fSrcBlend = kOne_GrBlendCoeff;
                 fDstBlend = kZero_GrBlendCoeff;
                 return GrXferProcessor::kIgnoreColor_OptFlag |
                        GrXferProcessor::kIgnoreCoverage_OptFlag;
             }
         }
     }  else {
         // check whether coverage can be safely rolled into alpha
         // of if we can skip color computation and just emit coverage
         if (can_tweak_alpha_for_coverage(fDstBlend)) {
-            return GrXferProcessor::kSetCoverageDrawing_OptFlag;
+            if (colorPOI.allStagesMultiplyInput()) {
+                return GrXferProcessor::kSetCoverageDrawing_OptFlag |
+                       GrXferProcessor::kCanTweakAlphaForCoverage_OptFlag;
+            } else {
+                return GrXferProcessor::kSetCoverageDrawing_OptFlag;
+
+            }
         }
         if (dstCoeffIsZero) {
             if (kZero_GrBlendCoeff == fSrcBlend) {
                 // the source color is not included in the blend
                 // the dst coeff is effectively zero so blend works out to:
                 // (c)(0)D + (1-c)D = (1-c)D.
                 fDstBlend = kISA_GrBlendCoeff;
                 return GrXferProcessor::kIgnoreColor_OptFlag |
                        GrXferProcessor::kSetCoverageDrawing_OptFlag;
             } else if (srcAIsOne) {
                 // the dst coeff is effectively zero so blend works out to:
                 // cS + (c)(0)D + (1-c)D = cS + (1-c)D.
                 // If Sa is 1 then we can replace Sa with c
                 // and set dst coeff to 1-Sa.
                 fDstBlend = kISA_GrBlendCoeff;
-                return GrXferProcessor::kSetCoverageDrawing_OptFlag;
+                if (colorPOI.allStagesMultiplyInput()) {
+                    return GrXferProcessor::kSetCoverageDrawing_OptFlag |
+                           GrXferProcessor::kCanTweakAlphaForCoverage_OptFlag;
+                } else {
+                    return GrXferProcessor::kSetCoverageDrawing_OptFlag;
+
+                }
             }
         } else if (dstCoeffIsOne) {
             // the dst coeff is effectively one so blend works out to:
             // cS + (c)(1)D + (1-c)D = cS + D.
             fDstBlend = kOne_GrBlendCoeff;
+            if (colorPOI.allStagesMultiplyInput()) {
+                return GrXferProcessor::kSetCoverageDrawing_OptFlag |
+                       GrXferProcessor::kCanTweakAlphaForCoverage_OptFlag;
+            } else {
+                return GrXferProcessor::kSetCoverageDrawing_OptFlag;
+
+            }
             return GrXferProcessor::kSetCoverageDrawing_OptFlag;
         }
     }
 
     return GrXferProcessor::kNone_Opt;
 }
 
 bool PorterDuffXferProcessor::hasSecondaryOutput() const {
     return kNone_SecondaryOutputType != fSecondaryOutputType;
 }
@@ skipping 239 matching lines @@
     } while (GrBlendCoeffRefsSrc(src));
 
     GrBlendCoeff dst;
     do {
         dst = GrBlendCoeff(random->nextRangeU(kFirstPublicGrBlendCoeff, kLastPublicGrBlendCoeff));
     } while (GrBlendCoeffRefsDst(dst));
 
     return GrPorterDuffXPFactory::Create(src, dst);
 }