Update //docs/callback.md for OnceCallback support of PostTask impls

Update //docs/callback.md for OnceCallback support of PostTask impls

This removes a mention to OnceCallback support of PostTask, since
PostTask does support OnceCallback now.

BUG=554299
Review-Url: https://codereview.chromium.org/2830223002
Cr-Commit-Position: refs/heads/master@{#466591}
Committed: https://chromium.googlesource.com/chromium/src/+/298f67afd032e7251a2b950715c456769d4977f9

[tzik, 2017-04-21 04:04:24]

Description was changed from

==========
Update //docs/callback.md for OnceCallback support of PostTask impls

BUG=
==========

to

==========
Update //docs/callback.md for OnceCallback support of PostTask impls

This removes a mention to OnceCallback support of PostTask, since
PostTask does support OnceCallback now.

BUG=554299
==========

[tzik, 2017-04-21 04:04:24]

tzik@chromium.org changed reviewers:
+ gab@chromium.org

[tzik, 2017-04-21 05:34:19]

gab: PTAL.
dgozman: FYI.

[gab, 2017-04-21 14:29:13]

lgtm

[tzik, 2017-04-24 06:04:56]

The CQ bit was checked by tzik@chromium.org

[commit-bot: I haz the power, 2017-04-24 06:05:06]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-24 06:14:16]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1493013896654380, "parent_rev":
"64c866e4041adcf57e6e86438482b2c030151f0d", "commit_rev":
"298f67afd032e7251a2b950715c456769d4977f9"}

[commit-bot: I haz the power, 2017-04-24 06:14:53]

Description was changed from

==========
Update //docs/callback.md for OnceCallback support of PostTask impls

This removes a mention to OnceCallback support of PostTask, since
PostTask does support OnceCallback now.

BUG=554299
==========

to

==========
Update //docs/callback.md for OnceCallback support of PostTask impls

This removes a mention to OnceCallback support of PostTask, since
PostTask does support OnceCallback now.

BUG=554299

Review-Url: https://codereview.chromium.org/2830223002
Cr-Commit-Position: refs/heads/master@{#466591}
Committed:
https://chromium.googlesource.com/chromium/src/+/298f67afd032e7251a2b950715c4...
==========

[commit-bot: I haz the power, 2017-04-24 06:14:54]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/298f67afd032e7251a2b950715c4...