This reverts commit c55429ac4937b912e42782ea6c95010a95f6d213.
Reasoning: The video has no height while the poster image is loading,
and then once it loads a moment later, it takes up extra space,
enlarges the video, and the page jumps. I don't know how to make the
page not jump while loading the poster. Width, height, and styles
look like they're set correctly.
de4438124a