Fix CodecSubset benches seg faults for kIndex8

bench/subset/SubsetSingleBench.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SubsetSingleBench.h"
 #include "SubsetBenchPriv.h"
 #include "SkData.h"
@@ skipping 52 matching lines @@
     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);
             SkAutoTDeleteArray<uint8_t> row(SkNEW_ARRAY(uint8_t, info.minRowBytes()));
             SkScanlineDecoder* scanlineDecoder = codec->getScanlineDecoder(
                     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();
             for (uint32_t y = 0; y < fSubsetHeight; y++) {
                 scanlineDecoder->getScanlines(row.get(), 1, 0);
                 memcpy(bitmap.getAddr(0, y), row.get() + fOffsetLeft * bpp,
                         fSubsetWidth * bpp);
             }
         }
     } else {
         for (int count = 0; count < n; count++) {
             SkAutoTDelete<SkImageDecoder> decoder(SkImageDecoder::Factory(fStream));
             int width, height;
             decoder->buildTileIndex(fStream->duplicate(), &width, &height);
             SkBitmap bitmap;
             SkIRect rect = SkIRect::MakeXYWH(fOffsetLeft, fOffsetTop, fSubsetWidth,
                     fSubsetHeight);
             decoder->decodeSubset(&bitmap, rect, fColorType);
         }
     }
 }