Add metrics for tracking LoginDatabase::Init failure.

Add metrics for tracking LoginDatabase::Init failure.

BUG=419070
Committed: https://crrev.com/8e0cdc35bc840eb9c1ccc058725ee6448f0972d8
Cr-Commit-Position: refs/heads/master@{#343353}

[vasilii, 2015-08-12 17:26:13]

vasilii@chromium.org changed reviewers:
+ isherman@chromium.org

[vasilii, 2015-08-12 17:26:13]

Hi Ilya,

please review.

[Ilya Sherman, 2015-08-13 00:34:18]

https://codereview.chromium.org/1285223002/diff/1/components/password_manager...
File components/password_manager/core/browser/login_database.cc (right):

https://codereview.chromium.org/1285223002/diff/1/components/password_manager...
components/password_manager/core/browser/login_database.cc:87: enum
DatabaseInitError {
Please document that this is used to back an UMA histogram, and therefore should
be treated as append-only.

https://codereview.chromium.org/1285223002/diff/1/components/password_manager...
components/password_manager/core/browser/login_database.cc:314: OPEN_FILE_ERROR,
DATABASE_INIT_ERROR_COUNT);
Please create a wrapper function for emitting to this histogram, so that you can
call it as "LogDatabaseInitError(OPEN_FILE_ERROR);".

https://codereview.chromium.org/1285223002/diff/1/components/password_manager...
components/password_manager/core/browser/login_database.cc:370:
meta_table_.GetVersionNumber(), 1, 30, 30);
nit: Would a sparse histogram be appropriate here?

https://codereview.chromium.org/1285223002/diff/1/tools/metrics/histograms/hi...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/1285223002/diff/1/tools/metrics/histograms/hi...
tools/metrics/histograms/histograms.xml:62348: +</enum>
When tracking errors, it's useful to include a bucket 0 that measures either "an
attempt was made" or "an attempt succeeded", so that you can compute an error
rate.  Otherwise, you can compare the frequency of errors relative to one
another, but you can't tell how frequently the operation fails overall.

[vasilii, 2015-08-13 09:04:33]

https://codereview.chromium.org/1285223002/diff/1/components/password_manager...
File components/password_manager/core/browser/login_database.cc (right):

https://codereview.chromium.org/1285223002/diff/1/components/password_manager...
components/password_manager/core/browser/login_database.cc:87: enum
DatabaseInitError {
On 2015/08/13 00:34:18, Ilya Sherman wrote:
> Please document that this is used to back an UMA histogram, and therefore
should
> be treated as append-only.

Done.

https://codereview.chromium.org/1285223002/diff/1/components/password_manager...
components/password_manager/core/browser/login_database.cc:314: OPEN_FILE_ERROR,
DATABASE_INIT_ERROR_COUNT);
On 2015/08/13 00:34:18, Ilya Sherman wrote:
> Please create a wrapper function for emitting to this histogram, so that you
can
> call it as "LogDatabaseInitError(OPEN_FILE_ERROR);".

Done.

https://codereview.chromium.org/1285223002/diff/1/components/password_manager...
components/password_manager/core/browser/login_database.cc:370:
meta_table_.GetVersionNumber(), 1, 30, 30);
On 2015/08/13 00:34:18, Ilya Sherman wrote:
> nit: Would a sparse histogram be appropriate here?

Done.

https://codereview.chromium.org/1285223002/diff/1/tools/metrics/histograms/hi...
File tools/metrics/histograms/histograms.xml (right):

https://codereview.chromium.org/1285223002/diff/1/tools/metrics/histograms/hi...
tools/metrics/histograms/histograms.xml:62348: +</enum>
On 2015/08/13 00:34:18, Ilya Sherman wrote:
> When tracking errors, it's useful to include a bucket 0 that measures either
"an
> attempt was made" or "an attempt succeeded", so that you can compute an error
> rate.  Otherwise, you can compare the frequency of errors relative to one
> another, but you can't tell how frequently the operation fails overall.

Done.

[Ilya Sherman, 2015-08-13 21:53:48]

LGTM, thanks.

[vasilii, 2015-08-14 08:22:51]

The CQ bit was checked by vasilii@chromium.org

[commit-bot: I haz the power, 2015-08-14 08:23:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1285223002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1285223002/20001

[commit-bot: I haz the power, 2015-08-14 08:27:05]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-08-14 08:27:54]

Patchset 2 (id:??) landed as
https://crrev.com/8e0cdc35bc840eb9c1ccc058725ee6448f0972d8
Cr-Commit-Position: refs/heads/master@{#343353}