add bench for mixers

Bug: skia:
Change-Id: I1b12c0deac802fb9da8bd285c1ff6d7e63da00f3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/201687
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
Auto-Submit: Mike Reed <reed@google.com>

bench/MixerBench.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2019 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "Benchmark.h"
+
+#include "SkCanvas.h"
+#include "SkMixer.h"
+#include "SkPaint.h"
+#include "SkShader.h"
+
+class MixerLerpBench : public Benchmark {
+public:
+    MixerLerpBench() {}
+
+protected:
+    const char* onGetName() override { return "mixer-lerp"; }
+
+    void onDelayedSetup() override {
+        auto s0 = SkShader::MakeColorShader(SK_ColorRED);
+        auto s1 = SkShader::MakeColorShader(SK_ColorBLUE);
+        auto mx = SkMixer::MakeShaderLerp(SkShader::MakeColorShader(0xFF880000));
+        fShader = SkShader::MakeMixer(s0, s1, mx);
+    }
+
+    void onDraw(int loops, SkCanvas* canvas) override {
+        const SkRect r = {0, 0, 256, 256};
+        SkPaint paint;
+        paint.setShader(fShader);
+        for (int j = 0; j < 100; ++j) {
+            for (int i = 0; i < loops; i++) {
+                canvas->drawRect(r, paint);
+            }
+        }
+    }
+
+private:
+    sk_sp<SkShader> fShader;
+    typedef Benchmark INHERITED;
+};
+DEF_BENCH( return new MixerLerpBench; )

gn/bench.gni

@@ -77,6 +77,7 @@ bench_sources = [
   "$_bench/MemsetBench.cpp",
   "$_bench/MergeBench.cpp",
   "$_bench/MipMapBench.cpp",
+  "$_bench/MixerBench.cpp",
   "$_bench/MorphologyBench.cpp",
   "$_bench/MutexBench.cpp",
   "$_bench/PatchBench.cpp",