Enable coverage when drawing to the stencil buffer.

src/gpu/GrDrawState.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDrawState.h"
 #include "GrPaint.h"
 
@@ skipping 309 matching lines @@
 
     bool covIsZero = !this->isCoverageDrawing() &&
                      !this->hasCoverageVertexAttribute() &&
                      0 == this->getCoverage();
     // When coeffs are (0,1) there is no reason to draw at all, unless
     // stenciling is enabled. Having color writes disabled is effectively
     // (0,1). The same applies when coverage is known to be 0.
     if ((kZero_GrBlendCoeff == *srcCoeff && dstCoeffIsOne) || covIsZero) {
         if (this->getStencil().doesWrite()) {
             return kDisableBlend_BlendOptFlag |
-                   kEmitTransBlack_BlendOptFlag;
+                   kEmitCoverage_BlendOptFlag;
         } else {
             return kSkipDraw_BlendOptFlag;
         }
     }
 
     // check for coverage due to constant coverage, per-vertex coverage, or coverage stage
     bool hasCoverage = forceCoverage ||
                        0xffffffff != this->getCoverage() ||
                        this->hasCoverageVertexAttribute() ||
                        fCoverageStages.count() > 0;
@@ skipping 134 matching lines @@
         fDrawState->fColorStages[s].saveCoordChange(&fSavedCoordChanges[i]);
         fDrawState->fColorStages[s].localCoordChange(coordChangeMatrix);
     }
 
     int numCoverageStages = fDrawState->numCoverageStages();
     for (int s = 0; s < numCoverageStages; ++s, ++i) {
         fDrawState->fCoverageStages[s].saveCoordChange(&fSavedCoordChanges[i]);
         fDrawState->fCoverageStages[s].localCoordChange(coordChangeMatrix);
     }
 }