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This fixes an issue where visibilitychange events were not properly
fired when the View was detached. A regression test has been added.

Bug: 1141093, 1058247
Change-Id: I4c35ff59182d42083647a7c2cc28aca7533ad936
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490234
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820417}