[NTP Snippets] Add histogram with fetch time

[NTP Snippets] Add histogram with fetch time

Client-side fetch latency can be useful to detect degradation in user
experience and release qualification (i.e. migration to new backend).

BUG=584428
Committed: https://crrev.com/5dce6eed8747d19117ab4d928caffbe9568bc830
Cr-Commit-Position: refs/heads/master@{#392569}

[mastiz, 2016-05-09 13:09:52]

mastiz@chromium.org changed reviewers:
+ treib@chromium.org

[Marc Treib, 2016-05-09 13:23:37]

lgtm

https://codereview.chromium.org/1961943002/diff/20001/components/ntp_snippets...
File components/ntp_snippets/ntp_snippets_fetcher_unittest.cc (right):

https://codereview.chromium.org/1961943002/diff/20001/components/ntp_snippets...
components/ntp_snippets/ntp_snippets_fetcher_unittest.cc:96: :
mock_task_runner_(new base::TestMockTimeTaskRunner()),
Ah, I didn't know about this. Nice!

[mastiz, 2016-05-09 13:29:27]

mastiz@chromium.org changed reviewers:
+ asvitkine@chromium.org

[mastiz, 2016-05-09 13:29:27]

asvitkine@chromium.org: please take a look. I was a little surprised that
kTestJsonParsingLatencyMs needs to be adjusted carefully to keep tests happy,
due to histogram bucket granularity.

It's tempting to use UMA_HISTOGRAM_CUSTOM_TIMES to achieve higher resolution in
the lower part of the spectrum but UMA_HISTOGRAM_TIMES seems common practice. Is
that reasonable?

[Alexei Svitkine (slow), 2016-05-09 16:27:47]

lgtm

[mastiz, 2016-05-10 07:23:56]

The CQ bit was checked by mastiz@chromium.org

[mastiz, 2016-05-10 07:23:56]

The patchset sent to the CQ was uploaded after l-g-t-m from treib@chromium.org,
asvitkine@chromium.org
Link to the patchset: https://codereview.chromium.org/1961943002/#ps60001
(title: "Rebased.")

[commit-bot: I haz the power, 2016-05-10 07:24:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1961943002/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1961943002/60001

[commit-bot: I haz the power, 2016-05-10 09:03:43]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2016-05-10 09:04:54]

Description was changed from

==========
[NTP Snippets] Add histogram with fetch time

Client-side fetch latency can be useful to detect degradation in user
experience and release qualification (i.e. migration to new backend).

BUG=584428
==========

to

==========
[NTP Snippets] Add histogram with fetch time

Client-side fetch latency can be useful to detect degradation in user
experience and release qualification (i.e. migration to new backend).

BUG=584428

Committed: https://crrev.com/5dce6eed8747d19117ab4d928caffbe9568bc830
Cr-Commit-Position: refs/heads/master@{#392569}
==========

[commit-bot: I haz the power, 2016-05-10 09:04:56]

Patchset 4 (id:??) landed as
https://crrev.com/5dce6eed8747d19117ab4d928caffbe9568bc830
Cr-Commit-Position: refs/heads/master@{#392569}