Add timing SkCodec to nanobench.

CodecBench:
Add new class for timing using SkCodec.

DecodingBench:
Include creating a decoder inside the loop. This is to have a better
comparison against SkCodec. SkCodec's factory function does not
necessarily read the same amount as SkImageDecoder's, so in order to
have a meaningful comparison, read the entire stream from the
beginning. Also for comparison, create a new SkStream from the
SkData each time.
Add a debugging check to make sure we have an SkImageDecoder.
Add include guards.

nanobench.cpp:
Decode using SkCodec.
When decoding using SkImageDecoder, exclude benches where we decoded
to a different color type than requested. SkImageDecoder may decide to
decode to a different type, in which case the name is misleading.

TODOs:
Now that we ignore color types that do not match the desired
color type, we should add Index8. This also means calling the more
complex version of getPixels so CodecBench can support kIndex8.

BUG=skia:3257

Review URL: https://codereview.chromium.org/1044363002

1 files changed, 39 insertions, 0 deletions

diff --git a/bench/CodecBench.h b/bench/CodecBench.h
new file mode 100644
index 0000000000..2bc4ba9a6f
--- /dev/null
+++ b/bench/CodecBench.h
@@ -0,0 +1,39 @@
+/*
+ * 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 "SkData.h"
+#include "SkImageInfo.h"
+#include "SkRefCnt.h"
+#include "SkString.h"
+
+/**
+ *  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;
+    SkAutoTUnref<SkData>    fData;
+    SkBitmap                fBitmap;
+    typedef Benchmark INHERITED;
+};
+#endif // CodecBench_DEFINED