The URI downloader is creating the source element with gst_element_factory_make() that returns a floating reference that nobody is consuming. This is causing problems in WebKit, where the smart pointers used to take references of the source elment get confused and end up consuming the floating reference and then releasing the element, which usually crashes because the URI downloader still tries to use its src element. See https://bugs.webkit.org/show_bug.cgi?id=144040.