Whenever the user interacts with an <input type='color' /> HTML element, WebKit will need to show a dialog to choose a color. For
that to happen in a general way, instead of just opening a ColorChooser (which might be not desirable in
some cases, which could prefer to use their own color chooser dialog), WebKit will fire the
run_color_chooser signal with a ColorChooserRequest
object, which will allow the client application to specify the color to be selected, to inspect the details of the request (e.g.
to get initial color) and to cancel the request, in case nothing was selected.
In case the client application does not wish to handle this signal, WebKit will provide a default handler which will asynchronously run a
regular ColorChooserDialog for the user to interact with.