The @identifier can be used afterwards to refer to the filter when using
webkit_user_content_filter_store_remove() and webkit_user_content_filter_store_load().
When the @identifier has been used in the past, the new filter source will replace
the one saved beforehand for the same identifier.
When the operation is finished, @callback will be invoked, which then can use
webkit_user_content_filter_store_save_finish() to obtain the resulting filter.
Asynchronously save a content filter from a source rule set in the WebKit content extesions JSON format.
The @identifier can be used afterwards to refer to the filter when using webkit_user_content_filter_store_remove() and webkit_user_content_filter_store_load(). When the @identifier has been used in the past, the new filter source will replace the one saved beforehand for the same identifier.
When the operation is finished, @callback will be invoked, which then can use webkit_user_content_filter_store_save_finish() to obtain the resulting filter.