added support for PLS path rendering

include/gpu/effects/GrCoverageSetOpXP.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrCoverageSetOpXP_DEFINED
 #define GrCoverageSetOpXP_DEFINED
 
@@ skipping 18 matching lines @@
 private:
     GrCoverageSetOpXPFactory(SkRegion::Op regionOp, bool invertCoverage);
 
     GrXferProcessor* onCreateXferProcessor(const GrCaps& caps,
                                            const GrPipelineOptimizations& optimizations,
                                            bool hasMixedSamples,
                                            const DstTexture*) const override;
 
     bool willReadDstColor(const GrCaps& /*caps*/,
                           const GrPipelineOptimizations& /*optimizations*/,
-                          bool /*hasMixedSamples*/) const override {
-        return false;
-    }
+                          bool /*hasMixedSamples*/) const override;
 
     bool onIsEqual(const GrXPFactory& xpfBase) const override {
         const GrCoverageSetOpXPFactory& xpf = xpfBase.cast<GrCoverageSetOpXPFactory>();
         return fRegionOp == xpf.fRegionOp;
     }
 
     GR_DECLARE_XP_FACTORY_TEST;
 
     SkRegion::Op fRegionOp;
     bool         fInvertCoverage;
 
     typedef GrXPFactory INHERITED;
 };
 #endif