Simplify flattening to just write enough to call the factory

src/core/SkXfermode_proccoeff.h

 #ifndef SkXfermode_proccoeff_DEFINED
 #define SkXfermode_proccoeff_DEFINED
 
 #include "SkXfermode.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
 
 struct ProcCoeff {
     SkXfermodeProc      fProc;
     SkXfermode::Coeff   fSC;
     SkXfermode::Coeff   fDC;
 };
 
 #define CANNOT_USE_COEFF    SkXfermode::Coeff(-1)
 
 class SK_API SkProcCoeffXfermode : public SkXfermode {
 public:
-    static SkProcCoeffXfermode* Create(const ProcCoeff& rec, Mode mode) {
-        return SkNEW_ARGS(SkProcCoeffXfermode, (rec, mode));
+    SkProcCoeffXfermode(const ProcCoeff& rec, Mode mode) {
+        fMode = mode;
+        fProc = rec.fProc;
+        // these may be valid, or may be CANNOT_USE_COEFF
+        fSrcCoeff = rec.fSC;
+        fDstCoeff = rec.fDC;
     }
-
+    
     virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,
                         const SkAlpha aa[]) const SK_OVERRIDE;
     virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count,
                         const SkAlpha aa[]) const SK_OVERRIDE;
     virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count,
                         const SkAlpha aa[]) const SK_OVERRIDE;
 
     virtual bool asMode(Mode* mode) const SK_OVERRIDE;
 
     virtual bool asCoeff(Coeff* sc, Coeff* dc) const SK_OVERRIDE;
 
 #if SK_SUPPORT_GPU
     virtual bool asNewEffect(GrEffect** effect,
                              GrTexture* background) const SK_OVERRIDE;
 #endif
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkProcCoeffXfermode)
 
 protected:
-    SkProcCoeffXfermode(const ProcCoeff& rec, Mode mode) {
-        fMode = mode;
-        fProc = rec.fProc;
-        // these may be valid, or may be CANNOT_USE_COEFF
-        fSrcCoeff = rec.fSC;
-        fDstCoeff = rec.fDC;
-    }
-
+#ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
     SkProcCoeffXfermode(SkReadBuffer& buffer);
+#endif
 
     virtual void flatten(SkWriteBuffer& buffer) const SK_OVERRIDE;
 
     Mode getMode() const { return fMode; }
 
     SkXfermodeProc getProc() const { return fProc; }
 
 private:
     SkXfermodeProc  fProc;
     Mode            fMode;
     Coeff           fSrcCoeff, fDstCoeff;
 
     typedef SkXfermode INHERITED;
 };
 
 #endif // #ifndef SkXfermode_proccoeff_DEFINED