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/BitmapRegionDecoderBench.cpp b/bench/BitmapRegionDecoderBench.cpp
new file mode 100644
index 0000000..77d3423
--- /dev/null
+++ b/bench/BitmapRegionDecoderBench.cpp
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "BitmapRegionDecoderBench.h"
+#include "CodecBenchPriv.h"
+#include "SkBitmap.h"
+#include "SkCodecTools.h"
+#include "SkOSFile.h"
+
+BitmapRegionDecoderBench::BitmapRegionDecoderBench(const char* baseName, SkData* encoded,
+        SkBitmapRegionDecoderInterface::Strategy strategy, SkColorType colorType,
+        uint32_t sampleSize, const SkIRect& subset)
+    : fBRD(nullptr)
+    , fData(SkRef(encoded))
+    , fStrategy(strategy)
+    , fColorType(colorType)
+    , fSampleSize(sampleSize)
+    , fSubset(subset)
+{
+    // Choose a useful name for the region decoding strategy
+    const char* strategyName;
+    switch (strategy) {
+        case SkBitmapRegionDecoderInterface::kOriginal_Strategy:
+            strategyName = "Original";
+            break;
+        case SkBitmapRegionDecoderInterface::kCanvas_Strategy:
+            strategyName = "Canvas";
+            break;
+        default:
+            SkASSERT(false);
+            strategyName = "";
+            break;
+    }
+
+    // Choose a useful name for the color type
+    const char* colorName = color_type_to_str(colorType);
+
+    fName.printf("BRD_%s_%s_%s", baseName, strategyName, colorName);
+    if (1 != sampleSize) {
+        fName.appendf("_%.3f", get_scale_from_sample_size(sampleSize));
+    }
+}
+
+const char* BitmapRegionDecoderBench::onGetName() {
+    return fName.c_str();
+}
+
+bool BitmapRegionDecoderBench::isSuitableFor(Backend backend) {
+    return kNonRendering_Backend == backend;
+}
+
+void BitmapRegionDecoderBench::onPreDraw() {
+    SkStreamRewindable* stream = new SkMemoryStream(fData);
+    fBRD.reset(SkBitmapRegionDecoderInterface::CreateBitmapRegionDecoder(stream, fStrategy));
+}
+
+void BitmapRegionDecoderBench::onDraw(const int n, SkCanvas* canvas) {
+    SkAutoTDelete<SkBitmap> bitmap;
+    for (int i = 0; i < n; i++) {
+        bitmap.reset(fBRD->decodeRegion(fSubset.left(), fSubset.top(), fSubset.width(),
+                fSubset.height(), fSampleSize, fColorType));
+        SkASSERT(nullptr != bitmap.get());
+    }
+}