Use fActualProc to choose fFastProc or fSlowProc in SkSwizzler

src/codec/SkSwizzler.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
 #include "SkOpts.h"
@@ skipping 751 matching lines @@
         srcWidth = frame->width();
     }
 
     return new SkSwizzler(fastProc, proc, ctable, srcOffset, srcWidth, dstOffset, dstWidth,
             srcBPP, dstBPP);
 }
 
 SkSwizzler::SkSwizzler(RowProc fastProc, RowProc proc, const SkPMColor* ctable, int srcOffset,
         int srcWidth, int dstOffset, int dstWidth, int srcBPP, int dstBPP)
     : fFastProc(fastProc)
-    , fProc(proc)
+    , fSlowProc(proc)
+    , fActualProc(fFastProc ? fFastProc : fSlowProc)
     , fColorTable(ctable)
     , fSrcOffset(srcOffset)
     , fDstOffset(dstOffset)
     , fSrcOffsetUnits(srcOffset * srcBPP)
     , fDstOffsetBytes(dstOffset * dstBPP)
     , fSrcWidth(srcWidth)
     , fDstWidth(dstWidth)
     , fSwizzleWidth(srcWidth)
     , fAllocatedWidth(dstWidth)
     , fSampleX(1)
     , fSrcBPP(srcBPP)
     , fDstBPP(dstBPP)
 {}
 
 int SkSwizzler::onSetSampleX(int sampleX) {
     SkASSERT(sampleX > 0); // Surely there is an upper limit? Should there be
                            // way to report failure?
     fSampleX = sampleX;
     fSrcOffsetUnits = (get_start_coord(sampleX) + fSrcOffset) * fSrcBPP;
     fDstOffsetBytes = (fDstOffset / sampleX) * fDstBPP;
     fSwizzleWidth = get_scaled_dimension(fSrcWidth, sampleX);
     fAllocatedWidth = get_scaled_dimension(fDstWidth, sampleX);
 
     // The optimized swizzler routines do not (yet) support sampling.
-    fFastProc = nullptr;
+    if (1 == fSampleX && fFastProc) {
+        fActualProc = fFastProc;
+    } else {
+        fActualProc = fSlowProc;
+    }
 
     return fAllocatedWidth;
 }
 
 void SkSwizzler::swizzle(void* dst, const uint8_t* SK_RESTRICT src) {
     SkASSERT(nullptr != dst && nullptr != src);
-    RowProc proc = fFastProc ? fFastProc : fProc;
-    proc(SkTAddOffset<void>(dst, fDstOffsetBytes), src, fSwizzleWidth, fSrcBPP,
+    fActualProc(SkTAddOffset<void>(dst, fDstOffsetBytes), src, fSwizzleWidth, fSrcBPP,
             fSampleX * fSrcBPP, fSrcOffsetUnits, fColorTable);
 }