Alter SkXfermode's asFragmentProcessor & asXPFactory contracts

src/core/SkXfermode_proccoeff.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 SkXfermode_proccoeff_DEFINED
 #define SkXfermode_proccoeff_DEFINED
 
@@ skipping 26 matching lines @@
     void xferA8(SkAlpha dst[], const SkPMColor src[], int count,
                 const SkAlpha aa[]) const override;
 
     bool asMode(Mode* mode) const override;
 
     bool supportsCoverageAsAlpha() const override;
 
     bool isOpaque(SkXfermode::SrcColorOpacity opacityType) const override;
 
 #if SK_SUPPORT_GPU
-    bool asFragmentProcessor(const GrFragmentProcessor**,
-                             const GrFragmentProcessor*) const override;
-
-    bool asXPFactory(GrXPFactory**) const override;
+    const GrFragmentProcessor* asFragmentProcessor(const GrFragmentProcessor*) const override;
+    GrXPFactory* asXPFactory() const override;
 #endif
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkProcCoeffXfermode)
 
 protected:
     void flatten(SkWriteBuffer& buffer) const override;
 
     Mode getMode() const { return fMode; }
 
     SkXfermodeProc getProc() const { return fProc; }
 
 private:
     SkXfermodeProc  fProc;
     Mode            fMode;
     Coeff           fSrcCoeff, fDstCoeff;
 
     friend class SkXfermode;
 
     typedef SkXfermode INHERITED;
 };
 
 #endif // #ifndef SkXfermode_proccoeff_DEFINED