Do not overwrite tab_state0 during multi-instance migration

Do not overwrite tab_state0 during multi-instance migration

During multi-instance migration, if tab_state0 already exists,
do not overwrite it by renaming tab_state. tab_state0 should not
already exist when multi-instance migration is run, but if it
does and it is overwritten then users may lose tabs.

BUG=649384
Committed: https://crrev.com/98219047ca2fc2a198f7268de4a3a106b09f7bc2
Cr-Commit-Position: refs/heads/master@{#420542}

[Theresa, 2016-09-22 18:16:57]

The CQ bit was checked by twellington@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-22 18:17:26]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Theresa, 2016-09-22 18:18:34]

twellington@chromium.org changed reviewers:
+ tedchoc@chromium.org

[Theresa, 2016-09-22 18:18:35]

ptal

[Theresa, 2016-09-22 18:43:42]

cc wnwen@

[commit-bot: I haz the power, 2016-09-22 18:45:57]

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

[commit-bot: I haz the power, 2016-09-22 18:45:58]

Dry run: This issue passed the CQ dry run.

[Peter Wen, 2016-09-22 19:38:40]

wnwen@chromium.org changed reviewers:
+ wnwen@chromium.org

[Peter Wen, 2016-09-22 19:38:41]

lgtm

Thanks for opening the bug and identifying this potential fix. We still don't
know what really happened for these users, so definitely more information is
needed to fix the root issue.

[Ted C, 2016-09-22 20:03:29]

lgtm

[Theresa, 2016-09-22 20:05:15]

The CQ bit was checked by twellington@chromium.org

[commit-bot: I haz the power, 2016-09-22 20:05:46]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Theresa, 2016-09-22 20:19:53]

twellington@chromium.org changed reviewers:
+ holte@google.com

[Theresa, 2016-09-22 20:19:54]

+holte@

ptal at actions.xml

[Theresa, 2016-09-22 20:20:08]

The CQ bit was unchecked by twellington@chromium.org

[commit-bot: I haz the power, 2016-09-22 20:20:16]

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

[commit-bot: I haz the power, 2016-09-22 20:20:16]

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

[Steven Holte, 2016-09-22 23:57:00]

holte@chromium.org changed reviewers:
+ holte@chromium.org

[Steven Holte, 2016-09-22 23:57:01]

This is OK, but why a UserAction instead of a histogram? This seems to be
recording the outcome of an action, rather than a new user action?

[Theresa, 2016-09-23 00:00:40]

On 2016/09/22 23:57:01, Steven Holte wrote:
> This is OK, but why a UserAction instead of a histogram? This seems to be
> recording the outcome of an action, rather than a new user action?

I'm trying to determine what percent of users are affected by these failure
cases. All users have to go through this migration path, so I don't really need
to count the non-failure cases. An action seemed like a simpler way to record
this but you are correct in that it is not a user-initiated action.

I can change them to histograms if that's more appropriate?

[Steven Holte, 2016-09-23 00:26:41]

On 2016/09/23 00:00:40, Theresa Wellington wrote:
> On 2016/09/22 23:57:01, Steven Holte wrote:
> > This is OK, but why a UserAction instead of a histogram? This seems to be
> > recording the outcome of an action, rather than a new user action?
> 
> I'm trying to determine what percent of users are affected by these failure
> cases. All users have to go through this migration path, so I don't really
need
> to count the non-failure cases. An action seemed like a simpler way to record
> this but you are correct in that it is not a user-initiated action.
> 
> I can change them to histograms if that's more appropriate?

Yes, I think a histogram is slightly more appropriate, since this isn't
user-initiated.

[Theresa, 2016-09-23 00:54:18]

On 2016/09/23 00:26:41, Steven Holte wrote:
> Yes, I think a histogram is slightly more appropriate, since this isn't
> user-initiated.

Done.

[Theresa, 2016-09-23 00:54:22]

The CQ bit was checked by twellington@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-23 00:54:47]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Steven Holte, 2016-09-23 01:06:40]

lgtm

[Theresa, 2016-09-23 01:14:45]

The CQ bit was unchecked by twellington@chromium.org

[Theresa, 2016-09-23 01:14:46]

The CQ bit was checked by twellington@chromium.org

[Theresa, 2016-09-23 01:14:46]

The patchset sent to the CQ was uploaded after l-g-t-m from
tedchoc@chromium.org, wnwen@chromium.org
Link to the patchset: https://codereview.chromium.org/2360183003/#ps10001
(title: "Record histograms instead of actions")

[commit-bot: I haz the power, 2016-09-23 01:14:53]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-23 02:09:23]

Committed patchset #2 (id:10001)

[commit-bot: I haz the power, 2016-09-23 02:11:46]

Description was changed from

==========
Do not overwrite tab_state0 during multi-instance migration

During multi-instance migration, if tab_state0 already exists,
do not overwrite it by renaming tab_state. tab_state0 should not
already exist when multi-instance migration is run, but if it
does and it is overwritten then users may lose tabs.

BUG=649384
==========

to

==========
Do not overwrite tab_state0 during multi-instance migration

During multi-instance migration, if tab_state0 already exists,
do not overwrite it by renaming tab_state. tab_state0 should not
already exist when multi-instance migration is run, but if it
does and it is overwritten then users may lose tabs.

BUG=649384

Committed: https://crrev.com/98219047ca2fc2a198f7268de4a3a106b09f7bc2
Cr-Commit-Position: refs/heads/master@{#420542}
==========

[commit-bot: I haz the power, 2016-09-23 02:11:48]

Patchset 2 (id:??) landed as
https://crrev.com/98219047ca2fc2a198f7268de4a3a106b09f7bc2
Cr-Commit-Position: refs/heads/master@{#420542}