Make GrGLShaderBuilder check whether GrEffect advertised that it would require the dst color or frag

src/gpu/GrDrawState.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDrawState_DEFINED
 #define GrDrawState_DEFINED
 
@@ skipping 435 matching lines @@
                 fStages[i].localCoordChange(oldToNew);
             }
         }
     }
 
     /**
      * Checks whether any of the effects will read the dst pixel color.
      */
     bool willEffectReadDst() const {
         for (int s = 0; s < kNumStages; ++s) {
-            if (this->isStageEnabled(s) && (*this->getStage(s).getEffect())->willReadDst()) {
+            if (this->isStageEnabled(s) && (*this->getStage(s).getEffect())->willReadDstColor()) {
                 return true;
             }
         }
         return false;
     }
 
     /// @}
 
     ///////////////////////////////////////////////////////////////////////////
     /// @name Coverage / Color Stages
@@ skipping 691 matching lines @@
      *  @param count      the number of attributes being set, limited to kMaxVertexAttribCnt.
      */
     void setVertexAttribs(const GrVertexAttrib attribs[], int count);
 
     typedef GrRefCnt INHERITED;
 };
 
 GR_MAKE_BITFIELD_OPS(GrDrawState::BlendOptFlags);
 
 #endif