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

tests/OnceTest.cpp

Index: tests/OnceTest.cpp
diff --git a/tests/OnceTest.cpp b/tests/OnceTest.cpp
index 35c2015166b98e9209ad9cf8fbf4aa858d65815f..3fd569a42aaa40ccae8a8261692395fc3b842bd8 100644
--- a/tests/OnceTest.cpp
+++ b/tests/OnceTest.cpp
@@ -32,7 +32,7 @@ SK_DECLARE_STATIC_ONCE(mt_once);
 DEF_TEST(SkOnce_Multithreaded, r) {
     int x = 0;
     // Run a bunch of tasks to be the first to add six to x.
-    sk_parallel_for(1021, [&](int) {
+    SkTaskGroup().batch(1021, [&](int) {
         void(*add_six)(int*) = [](int* p) { *p += 6; };
         SkOnce(&mt_once, add_six, &x);
     });