Move timeline get CSS AnimationPlayers W3C test into seperate file.

This test case fails in the Web Animations Polyfill (https://github.com/web-animations/web-animations-next) so we moved it to its own file. We don't want these tests to fork into a polyfill version and a blink version, so I'm replicating the change here.
BUG=

Review URL: https://codereview.chromium.org/650543004

git-svn-id: svn://svn.chromium.org/blink/trunk@184237 bbb929c8-8fbe-4397-9dbb-9b2b20218538