generalize xferu64 procs using proc4f

src/core/SkXfermode.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkXfermode.h"
 #include "SkXfermode_proccoeff.h"
 #include "SkColorPriv.h"
@@ skipping 1314 matching lines @@
 }
 
 SkXfermodeProc4f SkXfermode::GetProc4f(Mode mode) {
     SkXfermodeProc4f  proc = nullptr;
     if ((unsigned)mode < kModeCount) {
         proc = gProcCoeffs[mode].fProc4f;
     }
     return proc;
 }
 
+SkXfermodeProc4f SkXfermode::getProc4f() const {
+    Mode mode;
+    return this->asMode(&mode) ? GetProc4f(mode) : nullptr;
+}
+
 bool SkXfermode::ModeAsCoeff(Mode mode, Coeff* src, Coeff* dst) {
     SkASSERT(SK_ARRAY_COUNT(gProcCoeffs) == kModeCount);
 
     if ((unsigned)mode >= (unsigned)kModeCount) {
         // illegal mode parameter
         return false;
     }
 
     const ProcCoeff& rec = gProcCoeffs[mode];
 
@@ skipping 44 matching lines @@
     if (!xfer) {
         return SkXfermode::kOpaque_SrcColorOpacity == opacityType;
     }
 
     return xfer->isOpaque(opacityType);
 }
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkXfermode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkProcCoeffXfermode)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END