Almost done implementing idle. Just need to double check and test.
Trying to get event tests working.
Trying to get existing tests to pass.
Trying to track down why cancelling doesn't clear effects.
All tests are passing.
small changes
Removed comments
Idle state is working but other thigns are broken.

Mostly relate to currentTime returning NaN when player is idle,
and not clearing effects upon cancel.
playbackRate setter is refusing to work. I don't know why.
got play backwards after cancel to work.
Comments
Added some more tests and made them work.

Changes to match https://codereview.chromium.org/555063002.
Remove playbackRate setters. Will add them in a different patch.
Remove unneeded var
Small style change
Linter
Stop player.cancel() from nullifying the source. Need to fix broken tests.
No longer nulling animations on cancel. Needs tests!
removed comments
removed printlines