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..b5b560aefbffc4ee1e3fc516e47b4d30644035d3 100644
--- a/bench/subset/SubsetZoomBench.cpp
+++ b/bench/subset/SubsetZoomBench.cpp
@@ -77,7 +77,12 @@ 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));
+                if (kIndex_8_SkColorType == fColorType) {
+                    bitmap.allocPixels(info.makeWH(subsetWidth, subsetHeight), NULL,
+                            SkNEW_ARGS(SkColorTable, (colors, colorCount)));
+                } else {
+                    bitmap.allocPixels(info.makeWH(subsetWidth, subsetHeight));
+                }
 
                 uint32_t bpp = info.bytesPerPixel();
                 scanlineDecoder->skipScanlines(subsetStartY);