move SkProcCoeffXfermode unflatten constructor into .cpp, and range-check its mode

src/core/SkXfermode_proccoeff.h

 #ifndef SkXfermode_proccoeff_DEFINED
 #define SkXfermode_proccoeff_DEFINED
 
 #include "SkXfermode.h"
 #include "SkFlattenableBuffers.h"
 
 struct ProcCoeff {
     SkXfermodeProc      fProc;
     SkXfermode::Coeff   fSC;
     SkXfermode::Coeff   fDC;
 };
 
 #define CANNOT_USE_COEFF    SkXfermode::Coeff(-1)
 
-extern  const ProcCoeff gProcCoeffs[];
-
 class SkProcCoeffXfermode : public SkProcXfermode {
 public:
     SkProcCoeffXfermode(const ProcCoeff& rec, Mode mode)
             : INHERITED(rec.fProc) {
         fMode = mode;
         // these may be valid, or may be CANNOT_USE_COEFF
         fSrcCoeff = rec.fSC;
         fDstCoeff = rec.fDC;
     }
 
     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(GrEffectRef** effect,
                              GrTexture* background) const SK_OVERRIDE;
 #endif
 
     SK_DEVELOPER_TO_STRING()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkProcCoeffXfermode)
 
 protected:
-    SkProcCoeffXfermode(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {
-        fMode = (SkXfermode::Mode)buffer.read32();
-
-        const ProcCoeff& rec = gProcCoeffs[fMode];
-        // these may be valid, or may be CANNOT_USE_COEFF
-        fSrcCoeff = rec.fSC;
-        fDstCoeff = rec.fDC;
-        // now update our function-ptr in the super class
-        this->INHERITED::setProc(rec.fProc);
-    }
+    SkProcCoeffXfermode(SkFlattenableReadBuffer& buffer);
 
     virtual void flatten(SkFlattenableWriteBuffer& buffer) const SK_OVERRIDE;
 
     Mode getMode() const {
         return fMode;
     }
 
 private:
     Mode    fMode;
     Coeff   fSrcCoeff, fDstCoeff;
 
     typedef SkProcXfermode INHERITED;
 };
 
 #endif // #ifndef SkXfermode_proccoeff_DEFINED