Add nanobench tests for BitmapRegionDecoder

SkBitmapRegionDecoderInterface provides an interface
for multiple implementations of Android's
BitmapRegionDecoder.

We already have correctness tests in DM that will enable us
to compare the quality of our various BRD implementations.

We also need these performance tests to compare the speed
of our various implementations.

BUG=skia:4357

Review URL: https://codereview.chromium.org/1344993003
diff --git a/bench/CodecBenchPriv.h b/bench/CodecBenchPriv.h
new file mode 100644
index 0000000..d8585b6
--- /dev/null
+++ b/bench/CodecBenchPriv.h
@@ -0,0 +1,30 @@
+/*
+ * 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 CodecBenchPriv_DEFINED
+#define CodecBenchPriv_DEFINED
+
+#include "SkImageInfo.h"
+
+inline const char* color_type_to_str(SkColorType colorType) {
+    switch (colorType) {
+        case kN32_SkColorType:
+            return "N32";
+        case kRGB_565_SkColorType:
+            return "565";
+        case kGray_8_SkColorType:
+            return "Gray8";
+        case kIndex_8_SkColorType:
+            return "Index8";
+        case kAlpha_8_SkColorType:
+            return "Alpha8";
+        default:
+            return "Unknown";
+    }
+}
+
+#endif // CodecBenchPriv_DEFINED