Add Startup.TimeSinceLastStartup histogram.

Add Startup.TimeSinceLastStartup histogram.

This histogram shows the time between 2 consecutive startups.

BUG=547794
Committed: https://crrev.com/44cd7819dc6be0e640b6a1e03964d61210415a12
Cr-Commit-Position: refs/heads/master@{#368354}

[fdoray, 2016-01-05 20:15:23]

fdoray@chromium.org changed reviewers:
+ asvitkine@chromium.org, gab@chromium.org

[fdoray, 2016-01-05 20:15:23]

gab@ and asvitkine@: Can you review this CL? Thanks.

[Alexei Svitkine (slow), 2016-01-05 20:21:14]

https://codereview.chromium.org/1558203003/diff/1/components/startup_metric_u...
File components/startup_metric_utils/browser/startup_metric_utils.cc (right):

https://codereview.chromium.org/1558203003/diff/1/components/startup_metric_u...
components/startup_metric_utils/browser/startup_metric_utils.cc:107:
base::TimeDelta::FromDays(30).InMinutes(), 100)
Do you need 100 buckets? I think 50 should be sufficient.

You can look at the data for Variations.SeedFreshness to see the bucket ranges
there to see if that would be sufficient.

https://codereview.chromium.org/1558203003/diff/1/components/startup_metric_u...
components/startup_metric_utils/browser/startup_metric_utils.cc:501:
process_start_time - last_startup_timestamp;
In certain cases, you may get a negative value here - e.g. if system clock was
changed.

For UMA, this would result in going into the underflow bucket which is also the
0 bucket. Perhaps you don't want those samples there? Otherwise you'd be
conflating these two cases (0 minutes vs. clock skew).

[fdoray, 2016-01-05 20:36:14]

asvitkine@: Can you take another look?
gab@: Can you review this CL? 

I'll add a reviewer for chrome_browser_main.cc once I get your lgtms.

https://codereview.chromium.org/1558203003/diff/1/components/startup_metric_u...
File components/startup_metric_utils/browser/startup_metric_utils.cc (right):

https://codereview.chromium.org/1558203003/diff/1/components/startup_metric_u...
components/startup_metric_utils/browser/startup_metric_utils.cc:107:
base::TimeDelta::FromDays(30).InMinutes(), 100)
On 2016/01/05 20:21:14, Alexei Svitkine wrote:
> Do you need 100 buckets? I think 50 should be sufficient.
> 
> You can look at the data for Variations.SeedFreshness to see the bucket ranges
> there to see if that would be sufficient.

Done. I agree that 50 buckets is enough.

https://codereview.chromium.org/1558203003/diff/1/components/startup_metric_u...
components/startup_metric_utils/browser/startup_metric_utils.cc:501:
process_start_time - last_startup_timestamp;
On 2016/01/05 20:21:14, Alexei Svitkine wrote:
> In certain cases, you may get a negative value here - e.g. if system clock was
> changed.
> 
> For UMA, this would result in going into the underflow bucket which is also
the
> 0 bucket. Perhaps you don't want those samples there? Otherwise you'd be
> conflating these two cases (0 minutes vs. clock skew).

Done. We cannot conclude anything from negative values, so I changed the code to
ignore them.

[Alexei Svitkine (slow), 2016-01-05 20:42:57]

lgtm

[gab, 2016-01-06 19:26:17]

lgtm w/ nits, thanks!

https://codereview.chromium.org/1558203003/diff/20001/components/startup_metr...
File components/startup_metric_utils/browser/startup_metric_utils.h (right):

https://codereview.chromium.org/1558203003/diff/20001/components/startup_metr...
components/startup_metric_utils/browser/startup_metric_utils.h:48: // Registers
startup metric related prefs in |registry|.
s/startup metric related/startup related/ ?

https://codereview.chromium.org/1558203003/diff/20001/components/startup_metr...
components/startup_metric_utils/browser/startup_metric_utils.h:83: // Logs the
the Startup.TimeSinceLastStartup histogram. Obtains the timestamp of
"the the"

[fdoray, 2016-01-07 13:53:06]

https://codereview.chromium.org/1558203003/diff/20001/components/startup_metr...
File components/startup_metric_utils/browser/startup_metric_utils.h (right):

https://codereview.chromium.org/1558203003/diff/20001/components/startup_metr...
components/startup_metric_utils/browser/startup_metric_utils.h:48: // Registers
startup metric related prefs in |registry|.
On 2016/01/06 19:26:17, gab wrote:
> s/startup metric related/startup related/ ?

Done.

https://codereview.chromium.org/1558203003/diff/20001/components/startup_metr...
components/startup_metric_utils/browser/startup_metric_utils.h:83: // Logs the
the Startup.TimeSinceLastStartup histogram. Obtains the timestamp of
On 2016/01/06 19:26:16, gab wrote:
> "the the"

Done.

[fdoray, 2016-01-07 13:53:09]

The CQ bit was checked by fdoray@chromium.org

[fdoray, 2016-01-07 13:53:09]

The patchset sent to the CQ was uploaded after l-g-t-m from gab@chromium.org,
asvitkine@chromium.org
Link to the patchset: https://codereview.chromium.org/1558203003/#ps40001
(title: "Fix comments.")

[commit-bot: I haz the power, 2016-01-07 13:53:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1558203003/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1558203003/40001

[commit-bot: I haz the power, 2016-01-07 14:02:40]

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

[commit-bot: I haz the power, 2016-01-07 14:02:41]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[fdoray, 2016-01-07 14:05:32]

fdoray@chromium.org changed reviewers:
+ sky@chromium.org

[fdoray, 2016-01-07 14:05:33]

sky@chromium.org: Please review changes in chrome/browser/chrome_browser_main.cc

[sky, 2016-01-07 16:37:51]

LGTM

[fdoray, 2016-01-07 17:57:04]

fdoray@chromium.org changed reviewers:
+ caitkp@chromium.org

[fdoray, 2016-01-07 17:57:04]

caitkp@chromium.org: Please review changes in
components/startup_metric_utils.gypi

[Cait (Slow), 2016-01-07 22:07:47]

lgtm

[fdoray, 2016-01-07 22:26:51]

The CQ bit was checked by fdoray@chromium.org

[fdoray, 2016-01-07 22:26:51]

The patchset sent to the CQ was uploaded after l-g-t-m from gab@chromium.org,
asvitkine@chromium.org, sky@chromium.org
Link to the patchset: https://codereview.chromium.org/1558203003/#ps60001
(title: "Add base:prefs dependency.")

[commit-bot: I haz the power, 2016-01-07 22:27:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1558203003/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1558203003/60001

[commit-bot: I haz the power, 2016-01-07 22:49:19]

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

[commit-bot: I haz the power, 2016-01-07 22:49:20]

Try jobs failed on following builders:
  android_chromium_gn_compile_rel on tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_chro...)

[fdoray, 2016-01-08 14:20:25]

The CQ bit was checked by fdoray@chromium.org

[fdoray, 2016-01-08 14:20:25]

The patchset sent to the CQ was uploaded after l-g-t-m from gab@chromium.org,
asvitkine@chromium.org, sky@chromium.org, caitkp@chromium.org
Link to the patchset: https://codereview.chromium.org/1558203003/#ps80001
(title: "ifdef to fix build error on Android.")

[commit-bot: I haz the power, 2016-01-08 14:20:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1558203003/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1558203003/80001

[commit-bot: I haz the power, 2016-01-08 17:04:09]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2016-01-08 17:05:14]

Description was changed from

==========
Add Startup.TimeSinceLastStartup histogram.

This histogram shows the time between 2 consecutive startups.

BUG=547794
==========

to

==========
Add Startup.TimeSinceLastStartup histogram.

This histogram shows the time between 2 consecutive startups.

BUG=547794

Committed: https://crrev.com/44cd7819dc6be0e640b6a1e03964d61210415a12
Cr-Commit-Position: refs/heads/master@{#368354}
==========

[commit-bot: I haz the power, 2016-01-08 17:05:15]

Patchset 5 (id:??) landed as
https://crrev.com/44cd7819dc6be0e640b6a1e03964d61210415a12
Cr-Commit-Position: refs/heads/master@{#368354}