On some downstream platforms, the video gets black after playback finishes.

This happens because https://bugs.webkit.org/show_bug.cgi?id=89122 used to set the pipeline to NULL, although later https://bugs.webkit.org/show_bug.cgi?id=117354 set it to READY. This change deinitializes a big part of the pipeline, which should otherwise stay in a working state if the state was PLAUSED as it should be without those changes. While on desktop platforms the last video frame is still kept and shown, on some downstream platforms using a custom multimedia subsystem the deinitialization destroys internal resources and makes that last video frame not to be visible anymore.

The original purpose of the mentioned bugs was to avoid having the audio device opened after the video finished. This was relevant in 2012, when many platforms still used ALSA as a sound system, but it's not so relavant nowadays, when PulseAudio is the usual choice on desktop.