Fix for voice-over accessibility issue with tab switcher.

Fix for voice-over accessibility issue with tab switcher.

When a cell is removed from the collection view with a custom action,
the accessibility does not drop the custom action. This crashed the
application as the -deleteButtonPressedForCell: method assumed that
it would only ever be called with cell in the collection.

Work-around this by posting a UIAccessibilityScreenChangedNotification
which force accessibility to re-inspect everything (thus dropping the
selection custom action) and by also resetting the delegate on the cell
(not really necessary but cleaner).

BUG=677374
Review-Url: https://codereview.chromium.org/2615883002
Cr-Commit-Position: refs/heads/master@{#441649}
Committed: https://chromium.googlesource.com/chromium/src/+/e90f8871ccbf3df4fcef6960dd60756c559abcbe

[sdefresne, 2017-01-05 13:59:53]

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

[commit-bot: I haz the power, 2017-01-05 14:00:10]

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

[sdefresne, 2017-01-05 14:00:29]

sdefresne@chromium.org changed reviewers:
+ noyau@chromium.org

[sdefresne, 2017-01-05 14:00:29]

Please take a look.

[noyau (Ping after 24h), 2017-01-05 14:06:51]

lgtm. Thanks.

[commit-bot: I haz the power, 2017-01-05 14:12:11]

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

[commit-bot: I haz the power, 2017-01-05 14:12:12]

Dry run: This issue passed the CQ dry run.

[sdefresne, 2017-01-05 14:23:00]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2017-01-05 14:23:09]

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, 2017-01-05 14:26:33]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1483626180999290, "parent_rev":
"b0f63396085a5db6d6366668f84e8c166ee0247d", "commit_rev":
"e90f8871ccbf3df4fcef6960dd60756c559abcbe"}

[commit-bot: I haz the power, 2017-01-05 14:26:58]

Description was changed from

==========
Fix for voice-over accessibility issue with tab switcher.

When a cell is removed from the collection view with a custom action,
the accessibility does not drop the custom action. This crashed the
application as the -deleteButtonPressedForCell: method assumed that
it would only ever be called with cell in the collection.

Work-around this by posting a UIAccessibilityScreenChangedNotification
which force accessibility to re-inspect everything (thus dropping the
selection custom action) and by also resetting the delegate on the cell
(not really necessary but cleaner).

BUG=677374
==========

to

==========
Fix for voice-over accessibility issue with tab switcher.

When a cell is removed from the collection view with a custom action,
the accessibility does not drop the custom action. This crashed the
application as the -deleteButtonPressedForCell: method assumed that
it would only ever be called with cell in the collection.

Work-around this by posting a UIAccessibilityScreenChangedNotification
which force accessibility to re-inspect everything (thus dropping the
selection custom action) and by also resetting the delegate on the cell
(not really necessary but cleaner).

BUG=677374

Review-Url: https://codereview.chromium.org/2615883002
Cr-Commit-Position: refs/heads/master@{#441649}
Committed:
https://chromium.googlesource.com/chromium/src/+/e90f8871ccbf3df4fcef6960dd60...
==========

[commit-bot: I haz the power, 2017-01-05 14:26:59]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/e90f8871ccbf3df4fcef6960dd60...