If we swap its arguments, SkTaskGroup::batch() _is_ sk_parallel_for.

tests/BlendTest.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 "Test.h"
 #include "SkColor.h"
 #include "SkColorPriv.h"
@@ skipping 80 matching lines @@
             SkPMColor src = SkPackARGB32(sa, s, s, s),
                       dst = SkPackARGB32(da, d, d, d);
             xfermode->xfer32(&dst, &src, 1, nullptr);  // To keep it simple, no AA.
             if (!SkPMColorValid(dst)) {
                 ERRORF(r, "%08x is not premul using %s", dst, SkXfermode::ModeName(mode));
             }
         }}}}
     };
 
     // Parallelism helps speed things up on my desktop from ~725s to ~50s.
-    sk_parallel_for(SkXfermode::kLastMode, test_mode);
+    SkTaskGroup().batch(SkXfermode::kLastMode, test_mode);
 }