Last_n: do not delete the currently loading offline snapshot.

Last_n: do not delete the currently loading offline snapshot.

The code to delete existing offline pages created previously by last_n
was also causing the deletion of the very offline snapshot currently
being loaded. This change fixes that by verifying that the snapshot that
would be deleted is not the same as the one being loaded.

It also changes slightly the way the information of the lastest last_n
snapshot is cleared: now that only happens when the snapshot is actually
being deleted.

BUG=718212
Review-Url: https://codereview.chromium.org/2854213005
Cr-Commit-Position: refs/heads/master@{#469411}
Committed: https://chromium.googlesource.com/chromium/src/+/2319abbff11d73330235314486b7dec03f1b32e0

[carlosk, 2017-05-04 02:03:24]

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

[commit-bot: I haz the power, 2017-05-04 02:03:45]

Dry run: CQ is trying da patch.

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

[carlosk, 2017-05-04 02:07:38]

carlosk@chromium.org changed reviewers:
+ dewittj@chromium.org, dimich@chromium.org

[carlosk, 2017-05-04 02:07:38]

dewittj@, dimich@ PTAL.

[commit-bot: I haz the power, 2017-05-04 02:47:38]

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

[commit-bot: I haz the power, 2017-05-04 02:47:39]

Dry run: This issue passed the CQ dry run.

[Dmitry Titov, 2017-05-04 18:49:07]

lgtm

[carlosk, 2017-05-04 18:55:59]

The CQ bit was checked by carlosk@chromium.org

[commit-bot: I haz the power, 2017-05-04 18:56:46]

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, 2017-05-04 19:04:53]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1493924159327370, "parent_rev":
"f71a263681dc50097672cc55e0204c7b0e789a48", "commit_rev":
"2319abbff11d73330235314486b7dec03f1b32e0"}

[commit-bot: I haz the power, 2017-05-04 19:05:04]

Description was changed from

==========
Last_n: do not delete the currently loading offline snapshot.

The code to delete existing offline pages created previously by last_n
was also causing the deletion of the very offline snapshot currently
being loaded. This change fixes that by verifying that the snapshot that
would be deleted is not the same as the one being loaded.

It also changes slightly the way the information of the lastest last_n
snapshot is cleared: now that only happens when the snapshot is actually
being deleted.

BUG=718212
==========

to

==========
Last_n: do not delete the currently loading offline snapshot.

The code to delete existing offline pages created previously by last_n
was also causing the deletion of the very offline snapshot currently
being loaded. This change fixes that by verifying that the snapshot that
would be deleted is not the same as the one being loaded.

It also changes slightly the way the information of the lastest last_n
snapshot is cleared: now that only happens when the snapshot is actually
being deleted.

BUG=718212

Review-Url: https://codereview.chromium.org/2854213005
Cr-Commit-Position: refs/heads/master@{#469411}
Committed:
https://chromium.googlesource.com/chromium/src/+/2319abbff11d73330235314486b7...
==========

[commit-bot: I haz the power, 2017-05-04 19:05:06]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/2319abbff11d73330235314486b7...

[dewittj, 2017-05-04 19:45:26]

lgtm