Add timing SkCodec to nanobench.

bench/CodecBench.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 CodecBench_DEFINED
+#define CodecBench_DEFINED
+
+#include "Benchmark.h"
+#include "SkBitmap.h"
+#include "SkImageInfo.h"
+#include "SkStream.h"
+#include "SkString.h"
+
+class SkData;
+
+/**
+ *  Time SkCodec.
+ */
+class CodecBench : public Benchmark {
+public:
+    // Calls encoded->ref()
+    CodecBench(SkString basename, SkData* encoded, SkColorType colorType);
+
+protected:
+    const char* onGetName() override;
+    bool isSuitableFor(Backend backend) override;
+    void onDraw(const int n, SkCanvas* canvas) override;
+    void onPreDraw() override;
+
+private:
+    SkString                        fName;
+    const SkColorType               fColorType;
+    SkAutoTDelete<SkMemoryStream>   fStream;
+    SkBitmap                        fBitmap;
+    typedef Benchmark INHERITED;
+};
+#endif // CodecBench_DEFINED