When using WEBKIT_GST_USE_PLAYBIN3=1 and cog to open website with content <video src="./test.mp4" preload="auto" autoplay="autoplay" loop></video> the video would not be buffered into on-disk cache as it used to be with playbin(2). This is because playbin3 uridecodebin instantiated urisourcebin does not instantiate downloadbuffer element by default, this has to be explicitly enabled by setting the urisourcebin element 'download' parameter to TRUE.
Pull Request: https://github.com/WebKit/WebKit/pull/17915
Committed 268335@main (5d7c777b2c94): <https://commits.webkit.org/268335@main> Reviewed commits have been landed. Closing PR #17915 and removing active labels.
<rdar://problem/115911820>