[futex] Avoid accumulation errors in futex wait timeout

[futex] Avoid accumulation errors in futex wait timeout

The code previously used a relative timeout and accumulated wait times to see
if the timeout was exceeded. Now we convert the timeout into an absolute time,
and always compare the current time against that.

BUG=v8:4357
R=machenbach@chromium.org
LOG=n

Committed: https://crrev.com/ad1690d686575baadf8aa0fa820b0438e1a4b9a4
Cr-Commit-Position: refs/heads/master@{#30036}

[Michael Achenbach, 2015-08-05 19:54:37]

lgtm - thanks for fixing!

[Michael Achenbach, 2015-08-05 20:46:13]

FYI: I added the v8: prefix to the BUG= line. Otherwise it points into chromium
land.

[binji, 2015-08-05 20:55:59]

The CQ bit was checked by binji@chromium.org

[commit-bot: I haz the power, 2015-08-05 20:56:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1272733002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1272733002/1

[commit-bot: I haz the power, 2015-08-05 20:58:10]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-05 20:58:24]

Patchset 1 (id:??) landed as
https://crrev.com/ad1690d686575baadf8aa0fa820b0438e1a4b9a4
Cr-Commit-Position: refs/heads/master@{#30036}