Fix CodecSubset benches seg faults for kIndex8

bench/subset/SubsetZoomBench.cpp

Index: bench/subset/SubsetZoomBench.cpp
diff --git a/bench/subset/SubsetZoomBench.cpp b/bench/subset/SubsetZoomBench.cpp
index 3ce193b6ea8da33e7083da2c1e3386ea58ac2114..c911782039ef8f0992da6d42b9bb88dea5f3b7a2 100644
--- a/bench/subset/SubsetZoomBench.cpp
+++ b/bench/subset/SubsetZoomBench.cpp
@@ -77,7 +77,7 @@ void SubsetZoomBench::onDraw(const int n, SkCanvas* canvas) {
                 // Note that if we subsetted and scaled in a single step, we could use the
                 // same bitmap - as is often done in actual use cases.
                 SkBitmap bitmap;
-                bitmap.allocPixels(info.makeWH(subsetWidth, subsetHeight));
+                alloc_pixels(bitmap, fColorType, subsetWidth, subsetHeight, colors, colorCount);
 
                 uint32_t bpp = info.bytesPerPixel();
                 scanlineDecoder->skipScanlines(subsetStartY);