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This allows transitions on UiElements to leverage visibility animations.

Bug: None
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I5c362d2d6b90de5fa9702660ef7b3decaa0c0ff2
Reviewed-on: https://chromium-review.googlesource.com/579827
Commit-Queue: Ian Vollick <vollick@chromium.org>
Reviewed-by: Yash Malik <ymalik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488470}