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When the internal object is destroyed, notify the controller so it can
reset its internal state. It allows the user to close the window via any
system/window manager UI.

Bug: 863842
Change-Id: Ica84f4ffee2578658a60e0ae708a4e327d293077
Reviewed-on: https://chromium-review.googlesource.com/1147252Reviewed-by: Camille Lamy <clamy@chromium.org>
Reviewed-by: apacible <apacible@chromium.org>
Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577594}