It's unbearable that the user is put through a lengthy trial-and-error process in order to figure out which plugin he is missing for a particular video or audio. Webkit-GTK has to provide such information to the user, at the very least which codec (a/v) is attempted to be played and failed. Optionally, which plugin is require to play that specific codec. Optionall, Webkit-GTK should interface with the respective gstreamer functions to install that codec for the user by means of the correct package management system, with which gstreamer will interface.
For a start, such information could be written to stdout. Eventually, it should be correctly provided through a complete context menu and dialog which in turn is acessible by right-clicking the gstreamer frame.
*** This bug has been marked as a duplicate of bug 34085 ***