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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

Review URL: https://codereview.chromium.org/1038903003

Cr-Commit-Position: refs/heads/master@{#322432}