Fix CodecSubset benches seg faults for kIndex8

bench/subset/SubsetSingleBench.cpp

Index: bench/subset/SubsetSingleBench.cpp
diff --git a/bench/subset/SubsetSingleBench.cpp b/bench/subset/SubsetSingleBench.cpp
index 68c94cd246b125a27ba26e6bec7a2f6409006bb4..6c1da5c39e4db7210d90d5897e506321a7175464 100644
--- a/bench/subset/SubsetSingleBench.cpp
+++ b/bench/subset/SubsetSingleBench.cpp
@@ -70,7 +70,8 @@ void SubsetSingleBench::onDraw(const int n, SkCanvas* canvas) {
                     info, NULL, colors, &colorCount);
 
             SkBitmap bitmap;
-            bitmap.allocPixels(info.makeWH(fSubsetWidth, fSubsetHeight));
+            SkImageInfo subsetInfo = info.makeWH(fSubsetWidth, fSubsetHeight);
+            alloc_pixels(&bitmap, subsetInfo, colors, colorCount);
 
             scanlineDecoder->skipScanlines(fOffsetTop);
             uint32_t bpp = info.bytesPerPixel();