Add nanobench tests for BitmapRegionDecoder

bench/BitmapRegionDecoderBench.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef BitmapRegionDecoderBench_DEFINED
+#define BitmapRegionDecoderBench_DEFINED
+
+#include "Benchmark.h"
+#include "SkBitmapRegionDecoderInterface.h"
+#include "SkData.h"
+#include "SkImageInfo.h"
+#include "SkRefCnt.h"
+#include "SkString.h"
+
+/**
+ *  Time SkBitmapRegionDecoder.
+ *
+ *  The aim of this benchmark is not to duplicate the use cases that we test in the SubsetBenches.
+ *  Instead we assume that the SubsetBenches give us enough information to choose an appropriate
+ *  approach to subsetting.
+ *
+ *  This benchmark combines subsetting with scaling, allowing us to test the speed of several
+ *  different approaches to scaling while subsetting.
+ */
+class BitmapRegionDecoderBench : public Benchmark {
+public:
+    // Calls encoded->ref()
+    BitmapRegionDecoderBench(SkString basename, SkData* encoded,

[scroggo, 2015/09/17 20:05:38]

Probably want to use a const ref for basename. (Alternatively, we could use a
const char*)

[msarett, 2015/09/18 13:22:30]

I like const char*, since that is what we're using anyway.

+            SkBitmapRegionDecoderInterface::Strategy strategy, SkColorType colorType,
+            uint32_t sampleSize, const SkIRect& subset);
+
+protected:
+    const char* onGetName() override;
+    bool isSuitableFor(Backend backend) override;
+    void onDraw(const int n, SkCanvas* canvas) override;
+
+private:
+    SkString                                       fName;
+    SkAutoTUnref<SkData>                           fData;
+    const SkBitmapRegionDecoderInterface::Strategy fStrategy;
+    const SkColorType                              fColorType;
+    const uint32_t                                 fSampleSize;
+    const SkIRect                                  fSubset;
+    typedef Benchmark INHERITED;
+};
+#endif // BitmapRegionDecoderBench_DEFINED