Reland "Add pooling support on iOS."

This reverts commit f73091bb81fb3b0352f24a14479dba51069fdc8b.

Reason for revert: rolling forward after fixing prior CL

Original change's description:
> Revert "Add pooling support on iOS."
>
> This reverts commit 38a93e622b8cb6888d97551ac165406694342c7b.
>
> Reason for revert: need revert first pool change
>
> Original change's description:
> > Add pooling support on iOS.
> >
> > This replaces the `thread_local` attribute with `pthread_setspecific`
> > and `pthread_getspecific`. I don't have easy access to iOS 8/9 for
> > testing purposes, but on Mac OS X, this implementation works and
> > benchmarks the same as the `thread_local` implementation.
> >
> > Change-Id: I86db88c24d59d946adb66141b32733ebf5261c76
> > Reviewed-on: https://skia-review.googlesource.com/c/skia/+/328837
> > Reviewed-by: Brian Osman <brianosman@google.com>
> > Commit-Queue: Brian Osman <brianosman@google.com>
> > Auto-Submit: John Stiles <johnstiles@google.com>
>
> TBR=brianosman@google.com,adlai@google.com,johnstiles@google.com
>
> Change-Id: Ic06f9e32e524b2be601ee21a5da605fd19aaa64b
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/329164
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,brianosman@google.com,adlai@google.com,johnstiles@google.com

Change-Id: I0e021e9304ee88d6a29739c287eb515abff8b8a4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/329173
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
1 file changed