Create a scanline decoder without creating a codec

bench/subset/SubsetZoomBench.cpp

Index: bench/subset/SubsetZoomBench.cpp
diff --git a/bench/subset/SubsetZoomBench.cpp b/bench/subset/SubsetZoomBench.cpp
index 22bca23318bc2fd6c2c951f4e3b43e74e69a2ba0..84d50aa478ffd302e2520c11917a5b4df835fd1e 100644
--- a/bench/subset/SubsetZoomBench.cpp
+++ b/bench/subset/SubsetZoomBench.cpp
@@ -60,11 +60,11 @@ void SubsetZoomBench::onDraw(const int n, SkCanvas* canvas) {
     SkPMColor colors[256];
     if (fUseCodec) {
         for (int count = 0; count < n; count++) {
-            SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(fStream->duplicate()));
-            const SkImageInfo info = codec->getInfo().makeColorType(fColorType);
+            SkAutoTDelete<SkScanlineDecoder> scanlineDecoder(
+                    SkScanlineDecoder::NewFromStream(fStream->duplicate()));
+            const SkImageInfo info = scanlineDecoder->getInfo().makeColorType(fColorType);
             SkAutoTDeleteArray<uint8_t> row(SkNEW_ARRAY(uint8_t, info.minRowBytes()));
-            SkAutoTDelete<SkScanlineDecoder> scanlineDecoder(codec->getScanlineDecoder(
-                    info, NULL, colors, &colorCount));
+            scanlineDecoder->start(info, NULL, colors, &colorCount);
 
             const int centerX = info.width() / 2;
             const int centerY = info.height() / 2;