Adds a #WebKitUserContentFilter to the given #WebKitUserContentManager.
The same #WebKitUserContentFilter can be reused with multiple #WebKitUserContentManager instances.
Filters need to be saved and loaded from #WebKitUserContentFilterStore.
A #WebKitUserContentFilter
Adds a #WebKitUserContentFilter to the given #WebKitUserContentManager.
The same #WebKitUserContentFilter can be reused with multiple #WebKitUserContentManager instances.
Filters need to be saved and loaded from #WebKitUserContentFilterStore.