Enable tessellating GPU path renderer.

Enable tessellating GPU path renderer.

This also contains a fix to remove recursion from the sorted_merge()
step. This was essentially tail-recursion, and was causing stack
exhaustion on some platforms. Making it iterative fixes the issue.

Note: this CL will affect a large number of GPU GM results.

R=bsalomon@google.com
BUG=

Committed: https://skia.googlesource.com/skia/+/7ef63c85c5891ca59906e3c783a7f954be3f7f62

[Stephen White, 2015-04-13 20:59:58]

The CQ bit was checked by senorblanco@chromium.org

[Stephen White, 2015-04-13 21:00:15]

Brian: PTAL. Thanks!

[commit-bot: I haz the power, 2015-04-13 21:00:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1080113004/20001

[commit-bot: I haz the power, 2015-04-13 21:00:18]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-04-14 03:00 UTC

[Stephen White, 2015-04-13 21:00:29]

The CQ bit was unchecked by senorblanco@chromium.org

[Stephen White, 2015-04-13 21:01:38]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2015-04-13 21:02:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1080113004/40001

[commit-bot: I haz the power, 2015-04-13 21:02:06]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-04-14 03:02 UTC

[commit-bot: I haz the power, 2015-04-13 21:16:43]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-04-14 03:16 UTC

[bsalomon, 2015-04-13 21:26:12]

lgtm

[commit-bot: I haz the power, 2015-04-13 21:27:42]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/7ef63c85c5891ca59906e3c783a7f954be3f7f62