stages for most xfermodes

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 35 matching lines @@
 
 #if SK_SUPPORT_GPU
     sk_sp<GrFragmentProcessor> makeFragmentProcessorForImageFilter(
                                                         sk_sp<GrFragmentProcessor>) const override;
     sk_sp<GrXPFactory> asXPFactory() const override;
 #endif
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkProcCoeffXfermode)
 
+    bool onAppendStages(SkRasterPipeline*) const override;
+
 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