[Extensions] Add perf metrics for StartRequest()/HandleResponse()

[Extensions] Add perf metrics for StartRequest()/HandleResponse()

StartRequest() and HandleResponse() are used in the renderer to start
and finish an extension function call. The most intensive part of this
involves receiving arguments from v8 and converting them to base::Values
(or vice versa). Add a timer to see how long this takes.

Depending on the data, we may also want to break this into buckets and
record the function enum to highlight particularly egregious functions,
as we do for function execution time.

BUG=608561
Committed: https://crrev.com/b2b31390d6845f42b5966f854e90f69ff39705e0
Cr-Commit-Position: refs/heads/master@{#401462}

[Devlin, 2016-06-21 01:24:43]

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

[Devlin, 2016-06-21 01:24:43]

One more for y'all. :)

[lazyboy, 2016-06-21 02:23:02]

extensions lgtm.

[Mark P, 2016-06-22 22:06:43]

histograms.xml lgtm

[Devlin, 2016-06-22 22:27:05]

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

[commit-bot: I haz the power, 2016-06-22 22:27:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2088663002/1

[commit-bot: I haz the power, 2016-06-22 23:39:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-22 23:43:31]

Description was changed from

==========
[Extensions] Add perf metrics for StartRequest()/HandleResponse()

StartRequest() and HandleResponse() are used in the renderer to start
and finish an extension function call. The most intensive part of this
involves receiving arguments from v8 and converting them to base::Values
(or vice versa). Add a timer to see how long this takes.

Depending on the data, we may also want to break this into buckets and
record the function enum to highlight particularly egregious functions,
as we do for function execution time.

BUG=608561
==========

to

==========
[Extensions] Add perf metrics for StartRequest()/HandleResponse()

StartRequest() and HandleResponse() are used in the renderer to start
and finish an extension function call. The most intensive part of this
involves receiving arguments from v8 and converting them to base::Values
(or vice versa). Add a timer to see how long this takes.

Depending on the data, we may also want to break this into buckets and
record the function enum to highlight particularly egregious functions,
as we do for function execution time.

BUG=608561

Committed: https://crrev.com/b2b31390d6845f42b5966f854e90f69ff39705e0
Cr-Commit-Position: refs/heads/master@{#401462}
==========

[commit-bot: I haz the power, 2016-06-22 23:43:32]

Patchset 1 (id:??) landed as
https://crrev.com/b2b31390d6845f42b5966f854e90f69ff39705e0
Cr-Commit-Position: refs/heads/master@{#401462}