Clean up KeyboardVisibilityListener on InfobarContainer destruction

A bug was introduced in
https://chromium-review.googlesource.com/c/chromium/src/+/1346129
which caused InfobarContainer objects to be leaked after associated
tab is closed.
This patch adds code to remove the listener upon destroying
InfobarContainer objects.

R=fhorschig@chromium.org, mdjones@chromium.org

Bug: 940073
Change-Id: Idf9f765a191a99a574aca25259f4f50e1ff1318e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1516783
Reviewed-by: Friedrich [CET] <fhorschig@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#640952}
2 files changed