try Herb's new to_srgb

This was 6-8% faster than the previous code on my Trashcan.

Change-Id: I70081009e233c83226d6d302f871fb7e86cdc438
Reviewed-on: https://skia-review.googlesource.com/16986
Reviewed-by: Matt Sarett <msarett@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/bench/SkRasterPipelineBench.cpp b/bench/SkRasterPipelineBench.cpp
index f54efc5..527482a 100644
--- a/bench/SkRasterPipelineBench.cpp
+++ b/bench/SkRasterPipelineBench.cpp
@@ -125,3 +125,21 @@
     }
 };
 DEF_BENCH( return (new SkRasterPipeline_2dot2); )
+
+class SkRasterPipelineToSRGB : public Benchmark {
+public:
+    bool isSuitableFor(Backend backend) override { return backend == kNonRendering_Backend; }
+    const char* onGetName() override {
+        return "SkRasterPipeline_to_srgb";
+    }
+
+    void onDraw(int loops, SkCanvas*) override {
+        SkRasterPipeline p;
+        p.append(SkRasterPipeline::to_srgb);
+
+        while (loops --> 0) {
+            p.run(0,N);
+        }
+    }
+};
+DEF_BENCH( return (new SkRasterPipelineToSRGB); )