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This issue is caused by an ActionButtonVisibilityUpdate at
the end of SetIsPlaying - This will make all buttons invisible at the
beginning of a new media session when receiving
MediaSessionInfoChanged, then MediaSessionActionsChanged will update
button visibility immediately after that, which is causing the flashing
issue.

Bug: 1011160

Change-Id: I0f08fc77874641fd44025aae1c29f1cebeacdeb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1838385Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Jazz Xu <jazzhsu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704297}