Web Animations: Remove paused and finished from AnimationPlayer

Replaced by AnimationPlayer.playState

BUG=396366

Review URL: https://codereview.chromium.org/552933002

git-svn-id: svn://svn.chromium.org/blink/trunk@181592 bbb929c8-8fbe-4397-9dbb-9b2b20218538