Update XPF invariant info to not account for conflation

src/gpu/GrPipelineBuilder.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrPipelineBuilder_DEFINED
 #define GrPipelineBuilder_DEFINED
 
@@ skipping 121 matching lines @@
         int             fCoverageEffectCnt;
     };
 
     /// @}
 
     ///////////////////////////////////////////////////////////////////////////
     /// @name Blending
     ////
 
     /**
-     * This function returns true if the render target destination pixel values will be read for
-     * blending during draw.
+     * Returns true if this pipeline's color output will be affected by the existing render target
+     * destination pixel values (meaning we need to be careful with overlapping draws). Note that we
+     * can conflate coverage and color, so the destination color may still bleed into pixels that
+     * have partial coverage, even if this function returns false.
      */
-    bool willBlendWithDst(const GrPrimitiveProcessor*) const;
+    bool willColorBlendWithDst(const GrPrimitiveProcessor*) const;
 
     /**
      * Installs a GrXPFactory. This object controls how src color, fractional pixel coverage,
      * and the dst color are blended.
      */
     const GrXPFactory* setXPFactory(const GrXPFactory* xpFactory) {
         fXPFactory.reset(SkRef(xpFactory));
         return xpFactory;
     }
 
@@ skipping 224 matching lines @@
 
     void setClip(const GrClip& clip) { fClip = clip; }
     const GrClip& clip() const { return fClip; }
 
 private:
     // Calculating invariant color / coverage information is expensive, so we partially cache the
     // results.
     //
     // canUseFracCoveragePrimProc() - Called in regular skia draw, caches results but only for a
     //                                specific color and coverage.  May be called multiple times
-    // willBlendWithDst() - only called by Nvpr, does not cache results
+    // willColorBlendWithDst() - only called by Nvpr, does not cache results
     // GrOptDrawState constructor - never caches results
 
     /**
      * Primproc variants of the calc functions
      * TODO remove these when batch is everywhere
      */
     void calcColorInvariantOutput(const GrPrimitiveProcessor*) const;
     void calcCoverageInvariantOutput(const GrPrimitiveProcessor*) const;
 
     /**
@@ skipping 33 matching lines @@
     mutable GrProcOptInfo fCoverageProcInfo;
     mutable bool fColorProcInfoValid;
     mutable bool fCoverageProcInfoValid;
     mutable GrColor fColorCache;
     mutable GrColor fCoverageCache;
 
     friend class GrPipeline;
 };
 
 #endif