iOS: Fix runtime error in AppRTCMobile

iOS: Fix runtime error in AppRTCMobile

bugFix: `poping-up` alert message before `hanging-up` will result in runtime assertation as:
[Assert] Trying to dismiss the presentation controller while transitioning already.
Warning: Attempt to dismiss from view controller <UINavigationController: 0x13081e200> while a presentation or dismiss is in progress!
[Assert] transitionViewForCurrentTransition is not set, presentation controller was dismissed during the presentation? (<_UIAlertControllerAlertPresentationController: 0x12fd57bf0>)

BUG=webrtc:7569
Review-Url: https://codereview.webrtc.org/2863473005
Cr-Commit-Position: refs/heads/master@{#18190}
Committed: https://chromium.googlesource.com/external/webrtc/+/7cc881d190b27e57580dfa28c3102626b32fae22

[hewwatt, 2017-05-04 09:20:08]

Description was changed from

==========
bugFix: `poping-up` alert message before `hanging-up` will result in runtime
assertation as:
[Assert] Trying to dismiss the presentation controller while transitioning
already.
Warning: Attempt to dismiss from view controller <UINavigationController:
0x13081e200> while a presentation or dismiss is in progress!
[Assert] transitionViewForCurrentTransition is not set, presentation controller
was dismissed during the presentation?
(<_UIAlertControllerAlertPresentationController: 0x12fd57bf0>)

BUG=webrtc:7569
==========

to

==========
bugFix: `poping-up` alert message before `hanging-up` will result in runtime
assertation as:
[Assert] Trying to dismiss the presentation controller while transitioning
already.
Warning: Attempt to dismiss from view controller <UINavigationController:
0x13081e200> while a presentation or dismiss is in progress!
[Assert] transitionViewForCurrentTransition is not set, presentation controller
was dismissed during the presentation?
(<_UIAlertControllerAlertPresentationController: 0x12fd57bf0>)

BUG=webrtc:7569
==========

[hewwatt, 2017-05-04 09:22:13]

hewwatt@gmail.com changed reviewers:
+ kthelgason@webrtc.org, magjed@webrtc.org

[kthelgason, 2017-05-04 10:07:56]

The CQ bit was checked by kthelgason@webrtc.org to run a CQ dry run

[kthelgason, 2017-05-04 10:08:03]

lgtm

[commit-bot: I haz the power, 2017-05-04 10:08:06]

Dry run: CQ is trying da patch.

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

[commit-bot: I haz the power, 2017-05-04 10:29:06]

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

[commit-bot: I haz the power, 2017-05-04 10:29:07]

Dry run: This issue passed the CQ dry run.

[magjed_webrtc, 2017-05-04 12:26:06]

Description was changed from

==========
bugFix: `poping-up` alert message before `hanging-up` will result in runtime
assertation as:
[Assert] Trying to dismiss the presentation controller while transitioning
already.
Warning: Attempt to dismiss from view controller <UINavigationController:
0x13081e200> while a presentation or dismiss is in progress!
[Assert] transitionViewForCurrentTransition is not set, presentation controller
was dismissed during the presentation?
(<_UIAlertControllerAlertPresentationController: 0x12fd57bf0>)

BUG=webrtc:7569
==========

to

==========
iOS: Fix runtime error in AppRTCMobile

bugFix: `poping-up` alert message before `hanging-up` will result in runtime
assertation as:
[Assert] Trying to dismiss the presentation controller while transitioning
already.
Warning: Attempt to dismiss from view controller <UINavigationController:
0x13081e200> while a presentation or dismiss is in progress!
[Assert] transitionViewForCurrentTransition is not set, presentation controller
was dismissed during the presentation?
(<_UIAlertControllerAlertPresentationController: 0x12fd57bf0>)

BUG=webrtc:7569
==========

[magjed_webrtc, 2017-05-04 12:26:16]

lgtm

[kthelgason, 2017-05-18 08:15:01]

The CQ bit was checked by kthelgason@webrtc.org

[commit-bot: I haz the power, 2017-05-18 08:15:13]

CQ is trying da patch.

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

[commit-bot: I haz the power, 2017-05-18 08:33:35]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1495095301338440, "parent_rev":
"577f5dc60b2f129c947fce7a38597781282bf3a5", "commit_rev":
"7cc881d190b27e57580dfa28c3102626b32fae22"}

[commit-bot: I haz the power, 2017-05-18 08:33:39]

Description was changed from

==========
iOS: Fix runtime error in AppRTCMobile

bugFix: `poping-up` alert message before `hanging-up` will result in runtime
assertation as:
[Assert] Trying to dismiss the presentation controller while transitioning
already.
Warning: Attempt to dismiss from view controller <UINavigationController:
0x13081e200> while a presentation or dismiss is in progress!
[Assert] transitionViewForCurrentTransition is not set, presentation controller
was dismissed during the presentation?
(<_UIAlertControllerAlertPresentationController: 0x12fd57bf0>)

BUG=webrtc:7569
==========

to

==========
iOS: Fix runtime error in AppRTCMobile

bugFix: `poping-up` alert message before `hanging-up` will result in runtime
assertation as:
[Assert] Trying to dismiss the presentation controller while transitioning
already.
Warning: Attempt to dismiss from view controller <UINavigationController:
0x13081e200> while a presentation or dismiss is in progress!
[Assert] transitionViewForCurrentTransition is not set, presentation controller
was dismissed during the presentation?
(<_UIAlertControllerAlertPresentationController: 0x12fd57bf0>)

BUG=webrtc:7569

Review-Url: https://codereview.webrtc.org/2863473005
Cr-Commit-Position: refs/heads/master@{#18190}
Committed:
https://chromium.googlesource.com/external/webrtc/+/7cc881d190b27e57580dfa28c...
==========

[commit-bot: I haz the power, 2017-05-18 08:33:39]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/external/webrtc/+/7cc881d190b27e57580dfa28c...