Replace RenderArena with PartitionAlloc

Replace RenderArena with PartitionAlloc.

We believe this is memory positive, a very minor binary size saving, and perf neutral; see the bug for measurements. It's definitely a code clean-up. Perf bots will be carefully monitored after the land.

(This CL is mostly a subset of previously-reviewed https://codereview.chromium.org/16896019/, which we tried to land in a few pieces, to the limited extent possible.)

BUG=252057
R=abarth@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=155202

[Chris Evans, 2013-07-30 00:58:32]

I think I'm ready to give this a whirl when the tree is quiet?

[Chris Evans, 2013-07-30 01:25:15]

On 2013/07/30 00:58:32, Chris Evans wrote:
> I think I'm ready to give this a whirl when the tree is quiet?

Forgot to note: I fixed the comment from the original review, which noted that
RenderWidgetProtector might have degenerated to just a RefPtr. And indeed it
has, so it is gone.

[abarth-chromium, 2013-07-30 07:18:11]

Thanks for studying the performance of this change.  Elliot seems happy with
your results.  LGTM

[commit-bot: I haz the power, 2013-07-30 07:25:18]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/cevans@chromium.org/20231002/15001

[Chris Evans, 2013-07-30 07:27:24]

On 2013/07/30 07:25:18, I haz the power (commit-bot) wrote:
> CQ is trying da patch. Follow status at
> https://chromium-status.appspot.com/cq/cevans%40chromium.org/20231002/15001

(I removed the CQ, there's a compile error on the win try job due to my
over-optimistic use of "protected" instead of "public" for the visibility of
operator delete. I'll fix it tomorrow)

[commit-bot: I haz the power, 2013-07-30 19:01:31]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/cevans@chromium.org/20231002/36001

[commit-bot: I haz the power, 2013-07-30 19:07:24]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/cevans@chromium.org/20231002/36001

[commit-bot: I haz the power, 2013-07-30 23:44:40]

Retried try job too often on mac_blink_rel for step(s) webkit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_blink_...

[Chris Evans, 2013-07-31 02:21:20]

Committed patchset #8 manually as r155202 (presubmit successful).