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..697eabb75d5b79bc7ab6a2b34a612c37b5af9637 100644
--- a/bench/subset/SubsetSingleBench.cpp
+++ b/bench/subset/SubsetSingleBench.cpp
@@ -70,7 +70,12 @@ void SubsetSingleBench::onDraw(const int n, SkCanvas* canvas) {
                     info, NULL, colors, &colorCount);
 
             SkBitmap bitmap;
-            bitmap.allocPixels(info.makeWH(fSubsetWidth, fSubsetHeight));
+            if (kIndex_8_SkColorType == fColorType) {

[scroggo, 2015/06/30 16:40:19]

I agree that this is better (I think in patch set 1, we would leak the color
table in the case where it is not kIndex_8).

[msarett, 2015/06/30 18:40:28]

Acknowledged.

+                bitmap.allocPixels(info.makeWH(fSubsetWidth, fSubsetHeight), NULL,
+                        SkNEW_ARGS(SkColorTable, (colors, colorCount)));

[scroggo, 2015/06/30 16:40:19]

According to the documentation for tryAllocPixels (which allocPixels calls),

If the ImageInfo requires a colortable, then ColorTable must be non-null, and
will be ref'd.

Digging into the constructor of SkMallocPixelRef (which this eventually calls),
it is in fact ref'd. So this will lead to a memory leak.

You'll want to put your colortable into an SkAutoTUnref before passing it to
this function.

[msarett, 2015/06/30 18:40:27]

You're right.  Sorry should have put a little more thought into this.

+            } else {
+                bitmap.allocPixels(info.makeWH(fSubsetWidth, fSubsetHeight));
+            }
 
             scanlineDecoder->skipScanlines(fOffsetTop);
             uint32_t bpp = info.bytesPerPixel();