Add UMA for startup load time of component extensions. At the moment there is

Add more fine grained UMA for ExtensionService initialization time. At the
moment there is only total time and time to load all non-component extensions.
Time to load component extensions and time to notify all listeners is not
instrumented.

R=mek@chromium.org, mpearson@chromium.org
BUG=453073
Committed: https://crrev.com/fc4a9aaebb66e4f191bcd12f5d221a8e924c2c7a
Cr-Commit-Position: refs/heads/master@{#313615}

[Marijn Kruisselbrink, 2015-01-28 19:13:19]

https://codereview.chromium.org/883023003/diff/1/chrome/browser/extensions/co...
File chrome/browser/extensions/component_loader.cc (right):

https://codereview.chromium.org/883023003/diff/1/chrome/browser/extensions/co...
chrome/browser/extensions/component_loader.cc:128: base::Time start_time =
base::Time::Now();
Shouldn't this be base::TimeTicks::Now() just like below?

[Mark P, 2015-01-28 19:14:49]

https://codereview.chromium.org/883023003/diff/1/chrome/browser/extensions/co...
File chrome/browser/extensions/component_loader.cc (right):

https://codereview.chromium.org/883023003/diff/1/chrome/browser/extensions/co...
chrome/browser/extensions/component_loader.cc:135: base::TimeTicks::Now() -
start_time);
it probably would be better to use the same time format in, i.e., both timeticks

[not at google - send to devlin, 2015-01-28 19:29:00]

copy paste fail. will fix in a sec.

[not at google - send to devlin, 2015-01-28 21:21:02]

Patchset #2 (id:20001) has been deleted

[not at google - send to devlin, 2015-01-28 21:26:03]

Fixed, and I decided to add a second UMA right below that one (in the control
flow sense).

[not at google - send to devlin, 2015-01-28 21:26:08]

with a BUG

[Mark P, 2015-01-28 21:30:12]

histograms lgtm

https://codereview.chromium.org/883023003/diff/40001/chrome/browser/extension...
File chrome/browser/extensions/component_loader.cc (right):

https://codereview.chromium.org/883023003/diff/40001/chrome/browser/extension...
chrome/browser/extensions/component_loader.cc:129: base::TimeTicks start_time =
base::TimeTicks::Now();
nit: might as well be const

https://codereview.chromium.org/883023003/diff/40001/chrome/browser/extension...
File chrome/browser/extensions/extension_service.cc (right):

https://codereview.chromium.org/883023003/diff/40001/chrome/browser/extension...
chrome/browser/extensions/extension_service.cc:1411: base::TimeTicks start_time
= base::TimeTicks::Now();
nit: might as well be const

[not at google - send to devlin, 2015-01-28 21:39:50]

const'd

[Marijn Kruisselbrink, 2015-01-28 21:52:55]

lgtm

[not at google - send to devlin, 2015-01-28 21:55:24]

The CQ bit was checked by kalman@chromium.org

[commit-bot: I haz the power, 2015-01-28 21:55:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/883023003/60001

[commit-bot: I haz the power, 2015-01-28 23:30:51]

Committed patchset #3 (id:60001)

[commit-bot: I haz the power, 2015-01-28 23:32:31]

Patchset 3 (id:??) landed as
https://crrev.com/fc4a9aaebb66e4f191bcd12f5d221a8e924c2c7a
Cr-Commit-Position: refs/heads/master@{#313615}