Make SkColorTable explicitly thread-safe.

Make SkColorTable explicitly thread-safe.

Mostly this means using SkLazyPtr for the 16-bit cache.
We can remove the copy constructor now and just ref it instead.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/cc969c4dd936c97670788395c9cbee3f346e87d1

[mtklein, 2014-12-02 17:44:49]

mtklein@google.com changed reviewers:
+ mtklein@google.com, reed@google.com

[reed1, 2014-12-02 17:46:31]

lgtm w/ thought about const fields

https://codereview.chromium.org/769323002/diff/1/include/core/SkColorTable.h
File include/core/SkColorTable.h (right):

https://codereview.chromium.org/769323002/diff/1/include/core/SkColorTable.h#...
include/core/SkColorTable.h:60: int                                 fCount;
can we make fColors and fCount const?

[mtklein, 2014-12-02 17:51:18]

https://codereview.chromium.org/769323002/diff/1/include/core/SkColorTable.h
File include/core/SkColorTable.h (right):

https://codereview.chromium.org/769323002/diff/1/include/core/SkColorTable.h#...
include/core/SkColorTable.h:60: int                                 fCount;
On 2014/12/02 17:46:31, reed1 wrote:
> can we make fColors and fCount const?

Maybe, but it'll be an awkward enough rewrite of SkColorTable.cpp I'd want to
follow up.

The ugliest part is that it's sk_free(void*), not sk_free(const void*).  That's
actually all that prevents us from making f16BitCache const too.

[mtklein, 2014-12-02 17:51:27]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-12-02 17:52:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/769323002/1

[commit-bot: I haz the power, 2014-12-02 18:02:52]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/cc969c4dd936c97670788395c9cbee3f346e87d1