Fix a crash due to the modal signin being closed before being shown.

Fix a crash due to the modal signin being closed before being shown.

This prevents the browser from crashing at shutdown if it was closed
while the sync confirmation tab modal dialog was being laid out.

BUG=623466
Committed: https://crrev.com/f2c441c2115b7d8be8bab43ed6c787f4b466a90d
Cr-Commit-Position: refs/heads/master@{#402317}

[anthonyvd, 2016-06-27 19:12:04]

anthonyvd@chromium.org changed reviewers:
+ sky@chromium.org

[anthonyvd, 2016-06-27 19:12:05]

Hi sky@, can you please take a look at this crasher fix?

In some cases, PerformClose() could be called before DisplayModal() and
dereference a null modal_signin_widget_. Specifically, this was happening during
browser shutdown if the browser was closed between this delegate's creation and
the DisplayModal() call that happens after the layout of the sync confirmation
dialog's content.

Thanks!

[sky, 2016-06-27 20:38:43]

LGTM

[anthonyvd, 2016-06-27 20:40:55]

The CQ bit was checked by anthonyvd@chromium.org

[commit-bot: I haz the power, 2016-06-27 20:41:26]

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, 2016-06-27 22:41:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-27 22:43:25]

Description was changed from

==========
Fix a crash due to the modal signin being closed before being shown.

This prevents the browser from crashing at shutdown if it was closed
while the sync confirmation tab modal dialog was being laid out.

BUG=623466
==========

to

==========
Fix a crash due to the modal signin being closed before being shown.

This prevents the browser from crashing at shutdown if it was closed
while the sync confirmation tab modal dialog was being laid out.

BUG=623466

Committed: https://crrev.com/f2c441c2115b7d8be8bab43ed6c787f4b466a90d
Cr-Commit-Position: refs/heads/master@{#402317}
==========

[commit-bot: I haz the power, 2016-06-27 22:43:26]

Patchset 1 (id:??) landed as
https://crrev.com/f2c441c2115b7d8be8bab43ed6c787f4b466a90d
Cr-Commit-Position: refs/heads/master@{#402317}