Add new histograms to measure time in PreMainMessageLoop.

Add new histograms to measure time in PreMainMessageLoop.

I've identified areas which cause long delays through tracing and debugging, and want to collect metrics to see the effect in the wild. I've also added new trace events to match the new histograms.

BUG=454789
Committed: https://crrev.com/1b23b7d34f727d690cff990ef11a28513ce75ac4
Cr-Commit-Position: refs/heads/master@{#316284}

[rkaplow, 2015-02-13 17:52:26]

rkaplow@chromium.org changed reviewers:
+ asvitkine@chromium.org, thestig@chromium.org

[rkaplow, 2015-02-13 17:52:27]

asvitkine@chromium.org: Please review changes in 

thestig@chromium.org: Please review changes in

[Alexei Svitkine (slow), 2015-02-13 18:01:30]

https://codereview.chromium.org/922333002/diff/1/chrome/browser/browser_proce...
File chrome/browser/browser_process_impl.cc (right):

https://codereview.chromium.org/922333002/diff/1/chrome/browser/browser_proce...
chrome/browser/browser_process_impl.cc:1003:
"Startup.BrowserProcessImplPreMainMessageLoopRunTime");
Nit: To make these a bit more readable, how about adding an underscore between
the class and method name - i.e:

Startup.BrowserProcessImpl_PreMainMessageLoopRunTime

[Lei Zhang, 2015-02-13 18:34:48]

lgtm with the underscores in the name.

[rkaplow, 2015-02-13 18:41:51]

New patchsets have been uploaded after l-g-t-m from thestig@chromium.org

[rkaplow, 2015-02-13 18:44:24]

https://codereview.chromium.org/922333002/diff/1/chrome/browser/browser_proce...
File chrome/browser/browser_process_impl.cc (right):

https://codereview.chromium.org/922333002/diff/1/chrome/browser/browser_proce...
chrome/browser/browser_process_impl.cc:1003:
"Startup.BrowserProcessImplPreMainMessageLoopRunTime");
On 2015/02/13 18:01:30, Alexei Svitkine wrote:
> Nit: To make these a bit more readable, how about adding an underscore between
> the class and method name - i.e:
> 
> Startup.BrowserProcessImpl_PreMainMessageLoopRunTime

Done.

[Alexei Svitkine (slow), 2015-02-13 18:59:02]

lgtm

[rkaplow, 2015-02-13 19:00:05]

The CQ bit was checked by rkaplow@chromium.org

[commit-bot: I haz the power, 2015-02-13 19:01:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/922333002/20001

[commit-bot: I haz the power, 2015-02-13 20:15:19]

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

[commit-bot: I haz the power, 2015-02-13 20:15:20]

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

[rkaplow, 2015-02-13 20:18:01]

The CQ bit was checked by rkaplow@chromium.org

[commit-bot: I haz the power, 2015-02-13 20:19:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/922333002/20001

[commit-bot: I haz the power, 2015-02-13 20:53:03]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-13 20:54:20]

Patchset 2 (id:??) landed as
https://crrev.com/1b23b7d34f727d690cff990ef11a28513ce75ac4
Cr-Commit-Position: refs/heads/master@{#316284}