Currently changing the source of an HTML Video Element will not replace the custom controls visible on the window, if they have been set. Instead, this should set them back to the base state, where just play/pause and close are visible.

What steps will reproduce the problem?
(1) Start video.
(2) Enter PiP mode
(3) Change video

This can be experimented with at https://stevensawtelle.github.io/pictureinpicture/picture_in_picture_example.html by pressing the "Change Video" button.