Each section below has two boxes, the top runs on the main thread, the bottom
on the compositor.
This test is successful if the boxes are mostly in sync and all finish at the
same time.
Add second translate animation on timeout (with fill=forwards)
BLINK THREAD
IMPL THREAD
Add second translate animation on timeout if first one was paused earlier
BLINK THREAD
IMPL THREAD
Add second translate animation on timeout if first one was finished earlier
BLINK THREAD
IMPL THREAD
Add second translate animation on timeout if first higher-priority one was paused earlier
BLINK THREAD
IMPL THREAD