Use Sk4x to speed-up bounds of an array of points

BUG=skia:

Review URL: https://codereview.chromium.org/1015633004
diff --git a/bench/ScalarBench.cpp b/bench/ScalarBench.cpp
index 21f9264..f1a9b9a 100644
--- a/bench/ScalarBench.cpp
+++ b/bench/ScalarBench.cpp
@@ -152,7 +152,9 @@
     void onDraw(const int loops, SkCanvas* canvas) SK_OVERRIDE {
         SkRect r;
         for (int i = 0; i < loops; ++i) {
-            r.set(fPts, PTS);
+            for (int i = 0; i < 1000; ++i) {
+                r.set(fPts, PTS);
+            }
         }
     }