[Extensions] Add metrics for asynchronous port creation

[Extensions] Add metrics for asynchronous port creation

BUG=642380
Committed: https://crrev.com/4899757a47ed210d8290c81f2a02c0feeacea809
Cr-Commit-Position: refs/heads/master@{#418709}

[Devlin, 2016-09-13 17:51:09]

rdevlin.cronin@chromium.org changed reviewers:
+ lazyboy@chromium.org

[lazyboy, 2016-09-13 20:01:29]

lgtm.

[Devlin, 2016-09-13 23:03:09]

rdevlin.cronin@chromium.org changed reviewers:
+ mpearson@chromium.org

[Devlin, 2016-09-13 23:03:09]

Mark, mind taking a look at the histograms?

[Mark P, 2016-09-14 19:41:35]

histograms.xml lgtm

[Devlin, 2016-09-14 21:56:10]

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

[commit-bot: I haz the power, 2016-09-14 21:56:31]

Dry run: 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, 2016-09-14 22:51:04]

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

[commit-bot: I haz the power, 2016-09-14 22:51:05]

Dry run: This issue passed the CQ dry run.

[Devlin, 2016-09-14 22:53:48]

The CQ bit was checked by rdevlin.cronin@chromium.org

[Devlin, 2016-09-14 22:53:48]

The patchset sent to the CQ was uploaded after l-g-t-m from
lazyboy@chromium.org, mpearson@chromium.org
Link to the patchset: https://codereview.chromium.org/2337063003/#ps20001
(title: "Rebase")

[commit-bot: I haz the power, 2016-09-14 22:54:21]

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, 2016-09-14 23:00:19]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-09-14 23:03:48]

Description was changed from

==========
[Extensions] Add metrics for asynchronous port creation

BUG=642380
==========

to

==========
[Extensions] Add metrics for asynchronous port creation

BUG=642380

Committed: https://crrev.com/4899757a47ed210d8290c81f2a02c0feeacea809
Cr-Commit-Position: refs/heads/master@{#418709}
==========

[commit-bot: I haz the power, 2016-09-14 23:03:49]

Patchset 2 (id:??) landed as
https://crrev.com/4899757a47ed210d8290c81f2a02c0feeacea809
Cr-Commit-Position: refs/heads/master@{#418709}