SkLazyPtr, mk. 2

SkLazyPtr, mk. 2

SK_DECLARE_STATIC_LAZY_PTR and 
SK_DECLARE_STATIC_LAZY_PTR_ARRAY let you declare a single or
array of static pointers that are lazily initialized.

You can think of this as a restricted, lighter-weight
version of SkOnce.  There's no guarantee that Create will be
called exactly once, but we do guarantee all threads will
agree on the resulting pointer.

We'll clean up any other extra pointers we Create()ed by
calling Destroy(), which defaults to SkDELETE.  In debug
mode, we also clean up the winning pointer at process exit,
so we can make sure we didn't leak it or free it early.

I've ported SkData (singleton) and SkXfermode (array) as
examples.  Once this lands I'll port most other users of
SkOnce.

BUG=skia:

Committed: http://code.google.com/p/skia/source/detail?r=14976

[bungeman-skia, 2014-05-29 19:23:11]

lgtm

[mtklein, 2014-05-29 19:23:39]

On 2014/05/29 19:23:11, bungeman1 wrote:
> lgtm

+reed for include/

[mtklein, 2014-05-29 19:23:54]

+reed for include/ for real

[reed1, 2014-05-29 19:34:43]

lgtm

[mtklein, 2014-05-29 19:37:40]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-05-29 19:39:23]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/mtklein@chromium.org/306943003/40001

[commit-bot: I haz the power, 2014-05-29 19:43:32]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  Build-Ubuntu13.10-GCC4.8-x86_64-Release-Trybot on tryserver.chromium
(http://108.170.220.76:10117/builders/Build-Ubuntu13.10-GCC4.8-x86_64-Release-...)

[commit-bot: I haz the power, 2014-05-29 19:46:39]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-05-29 19:46:40]

Try jobs failed on following builders:
  Build-Ubuntu13.10-GCC4.8-x86_64-Release-Trybot on tryserver.chromium
(http://108.170.220.76:10117/builders/Build-Ubuntu13.10-GCC4.8-x86_64-Release-...)

[mtklein, 2014-05-29 19:58:37]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-05-29 19:59:59]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/mtklein@chromium.org/306943003/60001

[commit-bot: I haz the power, 2014-05-29 20:03:07]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  Build-Ubuntu13.10-GCC4.8-x86_64-Release-Trybot on tryserver.chromium
(http://108.170.220.76:10117/builders/Build-Ubuntu13.10-GCC4.8-x86_64-Release-...)

[mtklein, 2014-05-29 20:03:08]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-05-29 20:03:50]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/mtklein@chromium.org/306943003/70008

[commit-bot: I haz the power, 2014-05-29 20:13:27]

Change committed as 14976