Correct a possible free after use.

Correct a possible free after use.

This shows up in TSAN runs as a use-after-free warning.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/83e599a7ab49a9ef2e736d3d501b376f7b1993d6

[herb_g, 2015-09-10 20:08:52]

herb@google.com changed reviewers:
+ mtklein@google.com

[herb_g, 2015-09-10 20:09:04]

The CQ bit was checked by herb@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-09-10 20:09:10]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1333003002/2
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1333003002/2

[mtklein, 2015-09-10 20:17:33]

I don't think I understand the use-after-free and how this fixes it.  Walk me
through it?

[mtklein, 2015-09-10 20:35:47]

https://codereview.chromium.org/1333003002/diff/2/src/core/SkGlyphCache.cpp
File src/core/SkGlyphCache.cpp (right):

https://codereview.chromium.org/1333003002/diff/2/src/core/SkGlyphCache.cpp#n...
src/core/SkGlyphCache.cpp:433: AutoAcquire ac(globals.fLock);
Does this make sense?

// Do not lock globals.fLock here.
cache->fMapMutex.acquireShared();
if (!proc(cache, context)) {
   cache->fMapMutex.releaseShared();
   globals.attachCacheToHead(cache);
   return nullptr;
}
cache->fRefCount += 1;
globals.attachCacheToHead(cache);
return cache;

[mtklein, 2015-09-10 20:39:52]

lgtm as-is.  my question is follow-up-y.

[herb_g, 2015-09-10 20:46:05]

The CQ bit was unchecked by herb@google.com

[herb_g, 2015-09-10 20:46:06]

The CQ bit was checked by herb@google.com

[herb_g, 2015-09-10 20:46:10]

The CQ bit was checked by herb@google.com

[commit-bot: I haz the power, 2015-09-10 20:46:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1333003002/2
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1333003002/2

[commit-bot: I haz the power, 2015-09-10 21:16:15]

Committed patchset #2 (id:2) as
https://skia.googlesource.com/skia/+/83e599a7ab49a9ef2e736d3d501b376f7b1993d6