This test performs an animation of the left property with four different
fill modes. It animates over 0.1 second with a 0.1 second delay.
It takes snapshots at document load and the end of the animation.
None - from/to present
Backwards - from/to present
Forwards - from/to present
Both - from/to present
Both iterating - from/to present
None - from missing
Backwards - from missing
Forwards - from missing
Both - from missing
Both iterating - from missing