Add Precache.Fetch.Begin user action.

Add Precache.Fetch.Begin user action.

This marks the time (in control or enabled) when precaching begins,
allowing us to understand ordering with respect to other actions.

We are interested to see if we can draw any conclusions about the
NavigationToFirstContentfulPaint of the first pageload after a precache, using
a custom analysis of the logs. Histograms don't include a timestamp, so as an
approximation, we look at the timestamps of all user actions that occur in the
same log report as the histogram. This does an okay job of identifying the
timestamp of a pageload histogram, but as precaches do not accompany any user
actions, there often aren't any associated timestamps to use. This change adds
such an action.

BUG=

Review-Url: https://codereview.chromium.org/2806053002
Cr-Commit-Position: refs/heads/master@{#464791}
Committed: https://chromium.googlesource.com/chromium/src/+/14d5464e149236d40c40fe015ab10848f5a36d8d

[twifkak, 2017-04-07 23:23:20]

twifkak@chromium.org changed reviewers:
+ asvitkine@chromium.org, jamartin@chromium.org

[Alexei Svitkine (slow), 2017-04-10 19:04:10]

https://codereview.chromium.org/2806053002/diff/1/tools/metrics/actions/actio...
File tools/metrics/actions/actions.xml (right):

https://codereview.chromium.org/2806053002/diff/1/tools/metrics/actions/actio...
tools/metrics/actions/actions.xml:13841: A precache fetch was initiated, having
met all the necessary preconditions.
Please expand description to explain why this is needed as an action and not as
a histogram.

In general, for not user triggered things, histograms are preferred - unless you
want to do some kind of custom analysis. Can you detail this in the description?

[twifkak, 2017-04-11 01:09:29]

Description was changed from

==========
Add Precache.Fetch.Begin user action.

This marks the time (in control or enabled) when precaching begins,
allowing us to understand ordering with respect to other actions.

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

to

==========
Add Precache.Fetch.Begin user action.

This marks the time (in control or enabled) when precaching begins,
allowing us to understand ordering with respect to other actions.

We are interested to see if we can draw any conclusions about the
NavigationToFirstContentfulPaint of the first pageload after a precache, using
a custom analysis of the logs. Histograms don't include a timestamp, so as an
approximation, we look at the timestamps of all user actions that occur in the
same log report as the histogram. This does an okay job of identifying the
timestamp of a pageload histogram, but as precaches do not accompany any user
actions, there often aren't any associated timestamps to use. This change adds
such an action.

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

[twifkak, 2017-04-11 01:15:43]

https://codereview.chromium.org/2806053002/diff/1/tools/metrics/actions/actio...
File tools/metrics/actions/actions.xml (right):

https://codereview.chromium.org/2806053002/diff/1/tools/metrics/actions/actio...
tools/metrics/actions/actions.xml:13841: A precache fetch was initiated, having
met all the necessary preconditions.
On 2017/04/10 19:04:10, Alexei Svitkine (very slow) wrote:
> Please expand description to explain why this is needed as an action and not
as
> a histogram.
> 
> In general, for not user triggered things, histograms are preferred - unless
you
> want to do some kind of custom analysis. Can you detail this in the
description?

I added a bit of detail to the CL description. Let me know if you'd like more
detail on how the analysis is being done -- I can provide that offline.

I didn't add it to the description in the XML, because it seemed out of place
compared to other descriptions in this file. (And out of place for the UMA
frontend.) I'll add it if you feel otherwise, though.

[Alexei Svitkine (slow), 2017-04-11 20:52:20]

lgtm

[jamartin, 2017-04-14 19:57:08]

lgtm

[twifkak, 2017-04-14 20:06:37]

The CQ bit was checked by twifkak@chromium.org

[commit-bot: I haz the power, 2017-04-14 20:07:06]

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, 2017-04-14 20:48:18]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1492200397376130,
"parent_rev": "4246580ecc51331b116e65cdccab2c9b9b44b4c4", "commit_rev":
"14d5464e149236d40c40fe015ab10848f5a36d8d"}

[commit-bot: I haz the power, 2017-04-14 20:49:09]

Description was changed from

==========
Add Precache.Fetch.Begin user action.

This marks the time (in control or enabled) when precaching begins,
allowing us to understand ordering with respect to other actions.

We are interested to see if we can draw any conclusions about the
NavigationToFirstContentfulPaint of the first pageload after a precache, using
a custom analysis of the logs. Histograms don't include a timestamp, so as an
approximation, we look at the timestamps of all user actions that occur in the
same log report as the histogram. This does an okay job of identifying the
timestamp of a pageload histogram, but as precaches do not accompany any user
actions, there often aren't any associated timestamps to use. This change adds
such an action.

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

to

==========
Add Precache.Fetch.Begin user action.

This marks the time (in control or enabled) when precaching begins,
allowing us to understand ordering with respect to other actions.

We are interested to see if we can draw any conclusions about the
NavigationToFirstContentfulPaint of the first pageload after a precache, using
a custom analysis of the logs. Histograms don't include a timestamp, so as an
approximation, we look at the timestamps of all user actions that occur in the
same log report as the histogram. This does an okay job of identifying the
timestamp of a pageload histogram, but as precaches do not accompany any user
actions, there often aren't any associated timestamps to use. This change adds
such an action.

BUG=

Review-Url: https://codereview.chromium.org/2806053002
Cr-Commit-Position: refs/heads/master@{#464791}
Committed:
https://chromium.googlesource.com/chromium/src/+/14d5464e149236d40c40fe015ab1...
==========

[commit-bot: I haz the power, 2017-04-14 20:49:10]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/chromium/src/+/14d5464e149236d40c40fe015ab1...