Record the number of loaded profiles when a profile is erased from the profiles map kept by profile

Record the number of loaded profiles when a profile is erased from the profiles map kept by profile manager.

The reason behind is, UMA is observing a significant amount of times when GetLoadedProfiles returns an empty list (multiple times during one session). We hope that recording such a histogram would help to find out the reason for it, or at least eliminate one possibility.

BUG=412794
Committed: https://crrev.com/fedb226e68d4a2d587ec02ffdc35f82720e3134b
Cr-Commit-Position: refs/heads/master@{#297204}

[yao, 2014-09-26 17:42:49]

yiyaoliu@chromium.org changed reviewers:
+ asvitkine@chromium.org, noms@chromium.org

[Alexei Svitkine (slow), 2014-09-26 20:30:26]

https://codereview.chromium.org/605333002/diff/1/chrome/browser/profiles/prof...
File chrome/browser/profiles/profile_manager.cc (right):

https://codereview.chromium.org/605333002/diff/1/chrome/browser/profiles/prof...
chrome/browser/profiles/profile_manager.cc:960: profiles_info_.erase(iter);
If the plan is for this to be temporary, add a TODO here to remove it.

https://codereview.chromium.org/605333002/diff/1/chrome/browser/profiles/prof...
chrome/browser/profiles/profile_manager.cc:961:
UMA_HISTOGRAM_COUNTS("UMA.ProfilesCount", profiles_info_.size());
Let's do UMA_HISTOGRAM_COUNTS_100().

https://codereview.chromium.org/605333002/diff/1/tools/metrics/histograms/his...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/605333002/diff/1/tools/metrics/histograms/his...
tools/metrics/histograms/histograms.xml:35383: +<histogram
name="UMA.ProfilesCount">
Nit: How about a more specific name to match the description.

UMA.ProfilesCount.AfterDeletion

[yao, 2014-09-26 20:34:19]

Patchset #2 (id:20001) has been deleted

[yao, 2014-09-26 20:35:41]

https://codereview.chromium.org/605333002/diff/1/chrome/browser/profiles/prof...
File chrome/browser/profiles/profile_manager.cc (right):

https://codereview.chromium.org/605333002/diff/1/chrome/browser/profiles/prof...
chrome/browser/profiles/profile_manager.cc:960: profiles_info_.erase(iter);
On 2014/09/26 20:30:26, Alexei Svitkine wrote:
> If the plan is for this to be temporary, add a TODO here to remove it.

Done.

https://codereview.chromium.org/605333002/diff/1/chrome/browser/profiles/prof...
chrome/browser/profiles/profile_manager.cc:961:
UMA_HISTOGRAM_COUNTS("UMA.ProfilesCount", profiles_info_.size());
On 2014/09/26 20:30:26, Alexei Svitkine wrote:
> Let's do UMA_HISTOGRAM_COUNTS_100().

Done.

https://codereview.chromium.org/605333002/diff/1/tools/metrics/histograms/his...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/605333002/diff/1/tools/metrics/histograms/his...
tools/metrics/histograms/histograms.xml:35383: +<histogram
name="UMA.ProfilesCount">
On 2014/09/26 20:30:26, Alexei Svitkine wrote:
> Nit: How about a more specific name to match the description.
> 
> UMA.ProfilesCount.AfterDeletion

Done.

[Alexei Svitkine (slow), 2014-09-26 20:50:23]

LGTM

[noms (inactive), 2014-09-26 23:22:52]

lgtm.

please keep me posted on results. this is pretty baffling :)

[yao, 2014-09-29 13:18:31]

The CQ bit was checked by yiyaoliu@chromium.org

[commit-bot: I haz the power, 2014-09-29 13:19:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/605333002/40001

[commit-bot: I haz the power, 2014-09-29 14:55:01]

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

[commit-bot: I haz the power, 2014-09-29 14:55:02]

Try jobs failed on following builders:
  android_clang_dbg_recipe on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_clang_d...)

[yao, 2014-09-29 16:38:36]

The CQ bit was checked by yiyaoliu@chromium.org

[commit-bot: I haz the power, 2014-09-29 16:39:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/605333002/60001

[commit-bot: I haz the power, 2014-09-29 17:50:43]

Committed patchset #3 (id:60001) as ed4b8ce7c1ed63bf8d4476f728841d370b8188fe

[commit-bot: I haz the power, 2014-09-29 17:51:45]

Patchset 3 (id:??) landed as
https://crrev.com/fedb226e68d4a2d587ec02ffdc35f82720e3134b
Cr-Commit-Position: refs/heads/master@{#297204}