Check tabmodelselector null on reader mode callback

Check tabmodelselector null on reader mode callback

If the tab is reparented early on before this callback gets
back, we hit a NPE. For that callback early return if the
TabModelSelector is cleared

BUG=590673
Committed: https://crrev.com/d9aa65e5c27433343ebae98db2e23c0610590400
Cr-Commit-Position: refs/heads/master@{#378637}

[Yusuf, 2016-03-01 23:07:17]

yusufo@chromium.org changed reviewers:
+ dfalcantara@chromium.org

[gone, 2016-03-01 23:09:56]

lgtm

[Yusuf, 2016-03-01 23:10:25]

The CQ bit was checked by yusufo@chromium.org

[commit-bot: I haz the power, 2016-03-01 23:11:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1752123002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1752123002/20001

[Yusuf, 2016-03-01 23:26:33]

The CQ bit was unchecked by yusufo@chromium.org

[Yusuf, 2016-03-01 23:27:39]

yusufo@chromium.org changed reviewers:
+ mdjones@chromium.org

[mdjones, 2016-03-01 23:30:20]

lgtm

[mdjones, 2016-03-01 23:30:25]

The CQ bit was checked by mdjones@chromium.org

[mdjones, 2016-03-01 23:30:26]

The patchset sent to the CQ was uploaded after l-g-t-m from
dfalcantara@chromium.org
Link to the patchset: https://codereview.chromium.org/1752123002/#ps40001
(title: "Early return on request show panel")

[commit-bot: I haz the power, 2016-03-01 23:32:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1752123002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1752123002/40001

[commit-bot: I haz the power, 2016-03-02 00:56:32]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-03-02 00:58:07]

Description was changed from

==========
Check tabmodelselector null on reader mode callback

If the tab is reparented early on before this callback gets
back, we hit a NPE. For that callback early return if the
TabModelSelector is cleared

BUG=590673
==========

to

==========
Check tabmodelselector null on reader mode callback

If the tab is reparented early on before this callback gets
back, we hit a NPE. For that callback early return if the
TabModelSelector is cleared

BUG=590673

Committed: https://crrev.com/d9aa65e5c27433343ebae98db2e23c0610590400
Cr-Commit-Position: refs/heads/master@{#378637}
==========

[commit-bot: I haz the power, 2016-03-02 00:58:08]

Patchset 3 (id:??) landed as
https://crrev.com/d9aa65e5c27433343ebae98db2e23c0610590400
Cr-Commit-Position: refs/heads/master@{#378637}