Adding new benchmark to test image decoding performance.

bench/DecodingBench.cpp

+/*
+ * 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 "DecodingBench.h"
+#include "SkImageDecoder.h"
+#include "SkOSFile.h"
+
+/*
+ *
+ * This benchmark is designed to test the performance of image decoding.
+ * It is invoked from the nanobench.cpp file.
+ *
+ */
+DecodingBench::DecodingBench(SkString path, SkColorType colorType)
+    : fPath(path)
+    , fColorType(colorType)
+{
+    // Parse filename and the color type to give the benchmark a useful name
+    SkString baseName = SkOSPath::Basename(path.c_str());
+    const char* colorName;
+    switch(colorType) {
+    case kN32_SkColorType:

[scroggo, 2015/02/12 14:19:02]

Skia coding style dictates this should be indented from switch.

[msarett, 2015/02/12 18:52:56]

Done.

+        colorName = "N32";
+        break;
+    case kRGB_565_SkColorType:
+        colorName = "565";
+        break;
+    case kAlpha_8_SkColorType:
+        colorName = "Alpha8";
+        break;
+    default:
+        colorName = "Unknown";
+    }
+    fName.printf("Decode_%s_%s", baseName.c_str(), colorName);
+}
+
+const char* DecodingBench::onGetName() {
+    return fName.c_str();
+}
+
+bool DecodingBench::isSuitableFor(Backend backend) {
+    return kNonRendering_Backend == backend;
+}
+    
+void DecodingBench::onDraw(const int n, SkCanvas* canvas) {
+    // Decode each image file n times
+    for (int i = 0; i < n; i++) {
+        SkBitmap bitmap;
+        SkImageDecoder::DecodeFile(fPath.c_str(), &bitmap, fColorType,
+                                   SkImageDecoder::kDecodePixels_Mode);
+    }

[scroggo, 2015/02/12 14:19:02]

Didn't Mike suggest drawing to the canvas? Oh, I think that doesn't work since
we're only running this on the nonrendering backend. I guess that's a tradeoff
:(

[mtklein, 2015/02/12 14:41:38]

Yeah, I think in this case you'll find canvas is always NULL.  Don't draw on
that. :P

[msarett, 2015/02/12 18:52:56]

We discussed and decided it's best to use the non-rendering backend and not
draw.

+}