Determine whether we can tweakAlphaForCoverage during Pipeline/XP creation.

src/gpu/GrPipeline.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrPipeline.h"
 
 #include "GrBatch.h"
@@ skipping 84 matching lines @@
                                (pipelineBuilder.fCoverageStages[i]));
         usesLocalCoords = usesLocalCoords ||
                           pipelineBuilder.fCoverageStages[i].processor()->usesLocalCoords();
     }
 
     // let the GP init the batch tracker
     fInitBT.fColorIgnored = SkToBool(optFlags & GrXferProcessor::kIgnoreColor_OptFlag);
     fInitBT.fOverrideColor = fInitBT.fColorIgnored ? GrColor_ILLEGAL : overrideColor;
     fInitBT.fCoverageIgnored = SkToBool(optFlags & GrXferProcessor::kIgnoreCoverage_OptFlag);
     fInitBT.fUsesLocalCoords = usesLocalCoords;
+    fInitBT.fCanTweakAlphaForCoverage =
+        SkToBool(optFlags & GrXferProcessor::kCanTweakAlphaForCoverage_OptFlag);
 }
 
 void GrPipeline::adjustProgramFromOptimizations(const GrPipelineBuilder& pipelineBuilder,
                                                 GrXferProcessor::OptFlags flags,
                                                 const GrProcOptInfo& colorPOI,
                                                 const GrProcOptInfo& coveragePOI,
                                                 int* firstColorStageIdx,
                                                 int* firstCoverageStageIdx) {
     fReadsFragPosition = false;
 
@@ skipping 34 matching lines @@
     SkASSERT(this->numFragmentStages() == that.numFragmentStages());
     for (int i = 0; i < this->numFragmentStages(); i++) {
 
         if (this->getFragmentStage(i) != that.getFragmentStage(i)) {
             return false;
         }
     }
     return true;
 }