Implement four more xfermodes with Sk4px.

src/opts/SkXfermode_opts_SSE2.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkColorPriv.h"
 #include "SkColor_opts_SSE2.h"
 #include "SkMathPriv.h"
@@ skipping 497 matching lines @@
 
 #ifndef SK_IGNORE_TO_STRING
 void SkSSE2ProcCoeffXfermode::toString(SkString* str) const {
     this->INHERITED::toString(str);
 }
 #endif
 
 SkProcCoeffXfermode* SkPlatformXfermodeFactory_impl_SSE2(const ProcCoeff& rec,
                                                          SkXfermode::Mode mode) {
     SkXfermodeProcSIMD proc = nullptr;
-    // TODO(mtklein): implement these Sk4px.
     switch (mode) {
+        // TODO(mtklein): Sk4pxXfermode has these now.  Clean up.
         case SkProcCoeffXfermode::kOverlay_Mode:    proc =    overlay_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kDarken_Mode:     proc =     darken_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kLighten_Mode:    proc =    lighten_modeproc_SSE2; break;
+        case SkProcCoeffXfermode::kHardLight_Mode:  proc =  hardlight_modeproc_SSE2; break;
+
+        // TODO(mtklein): implement these with SkPMFloat.
+        case SkProcCoeffXfermode::kSoftLight_Mode:  proc =  softlight_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kColorDodge_Mode: proc = colordodge_modeproc_SSE2; break;
         case SkProcCoeffXfermode::kColorBurn_Mode:  proc =  colorburn_modeproc_SSE2; break;
-        case SkProcCoeffXfermode::kHardLight_Mode:  proc =  hardlight_modeproc_SSE2; break;
-        case SkProcCoeffXfermode::kSoftLight_Mode:  proc =  softlight_modeproc_SSE2; break;
         default: break;
     }
     return proc ? SkNEW_ARGS(SkSSE2ProcCoeffXfermode, (rec, mode, (void*)proc)) : nullptr;
 }