Web Animations: Avoid player updates when compositor start time is set

Player updates were being forced following start time updates, this could cause
invalid lifecycle changes in some cases. By setting the player outdated this
can be avoided.

BUG=364250

Review URL: https://codereview.chromium.org/238353013

git-svn-id: svn://svn.chromium.org/blink/trunk@171839 bbb929c8-8fbe-4397-9dbb-9b2b20218538