Fix crash occurring during infobar dismissal at BVC deletion.

Fix crash occurring during infobar dismissal at BVC deletion.

Calling the InfoBarContainerIOS destructor leads to the removal of infobars via
|InfoBarContainerIOS::PlatformSpecificRemoveInfoBar|, which leads to the BVC
wanting to change the InfoBarContainerIOS's height (in |infoBarContainerStateChanged|)
This leads to a crash because the InfoBarContainerIOS is in the process of
being deleted.

This CL makes the flow abort early.

BUG=448093
Committed: https://crrev.com/695932863ee381ddcb55a61eae9e5f0623df9138
Cr-Commit-Position: refs/heads/master@{#322432}

[jif-google, 2015-03-26 17:39:10]

Patchset #2 (id:20001) has been deleted

[jif-google, 2015-03-26 17:48:50]

jif@google.com changed reviewers:
+ droger@chromium.org

[jif, 2015-03-26 17:49:22]

ptal

[droger, 2015-03-26 17:57:32]

lgtm

[jif-google, 2015-03-26 17:57:56]

The CQ bit was checked by jif@google.com

[commit-bot: I haz the power, 2015-03-26 17:58:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1038903003/40001

[commit-bot: I haz the power, 2015-03-26 18:27:48]

Committed patchset #2 (id:40001)

[commit-bot: I haz the power, 2015-03-26 18:28:59]

Patchset 2 (id:??) landed as
https://crrev.com/695932863ee381ddcb55a61eae9e5f0623df9138
Cr-Commit-Position: refs/heads/master@{#322432}