Update some Sk4px APIs.

tests/SkNxTest.cpp

Index: tests/SkNxTest.cpp
diff --git a/tests/SkNxTest.cpp b/tests/SkNxTest.cpp
index eab625d41e3fe2f6e71d2ac2e4658850d9859e2a..3719044025e7a145ae43a2504d4a34d58c66c015 100644
--- a/tests/SkNxTest.cpp
+++ b/tests/SkNxTest.cpp
@@ -174,15 +174,15 @@ DEF_TEST(Sk4px_muldiv255round, r) {
         int exact = (a*b+127)/255;
 
         // Duplicate a and b 16x each.
-        Sk4px av((SkAlpha)a),
-              bv((SkAlpha)b);
+        auto av = Sk4px::DupAlpha(a),
+             bv = Sk4px::DupAlpha(b);
 
         // This way should always be exactly correct.
-        int correct = av.mulWiden(bv).div255RoundNarrow().kth<0>();
+        int correct = (av * bv).div255().kth<0>();
         REPORTER_ASSERT(r, correct == exact);
 
         // We're a bit more flexible on this method: correct for 0 or 255, otherwise off by <=1.
-        int fast = av.fastMulDiv255Round(bv).kth<0>();
+        int fast = av.approxMulDiv255(bv).kth<0>();
         REPORTER_ASSERT(r, fast-exact >= -1 && fast-exact <= 1);
         if (a == 0 || a == 255 || b == 0 || b == 255) {
             REPORTER_ASSERT(r, fast == exact);