SkPath::fFirstDirection: seq-cst -> relaxed

SkPath::fFirstDirection: seq-cst -> relaxed

We landed this originally with lazily-correct sequentially-consistent memory
order.  It turns out that's regressed performance, we think particularly when
recording paths.  We also think there's no need for anything but relaxed memory
order here.

We should see this chart go down if all goes well: https://perf.skia.org/#4329
There are also Chrome performance charts to watch in the linked bug.

BUG=chromium:537700
CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-TSAN-Trybot,Test-Ubuntu-GCC-Golo-GPU-GT610-x86_64-Release-TSAN

No public API changes.
TBR=reed@google.com

Committed: https://skia.googlesource.com/skia/+/bf90520f63415f539cd5792a18efbd79cb86be0a

[mtklein_C, 2015-10-07 17:29:47]

The CQ bit was checked by mtklein@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-07 17:29:55]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1393833003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1393833003/1

[mtklein_C, 2015-10-07 17:36:49]

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

[commit-bot: I haz the power, 2015-10-07 17:41:59]

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

[commit-bot: I haz the power, 2015-10-07 17:42:00]

Dry run: This issue passed the CQ dry run.

[mtklein_C, 2015-10-07 17:42:13]

The CQ bit was checked by mtklein@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-07 17:42:34]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1393833003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1393833003/1

[herb_g, 2015-10-07 18:39:11]

lgtm

[mtklein, 2015-10-07 18:39:36]

The CQ bit was unchecked by mtklein@google.com

[mtklein, 2015-10-07 18:39:40]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-10-07 18:39:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1393833003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1393833003/1

[commit-bot: I haz the power, 2015-10-07 18:41:37]

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

[commit-bot: I haz the power, 2015-10-07 18:41:37]

Try jobs failed on following builders:
  skia_presubmit-Trybot on client.skia.fyi (JOB_FAILED,
http://build.chromium.org/p/client.skia.fyi/builders/skia_presubmit-Trybot/bu...)

[mtklein, 2015-10-07 19:00:38]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-10-07 19:00:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1393833003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1393833003/1

[commit-bot: I haz the power, 2015-10-07 19:46:48]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/bf90520f63415f539cd5792a18efbd79cb86be0a