By default it still uses PrefixSearch and supports PrefixSearchBackend
but it can be deprecated and phased out and SearchEngine extensions used
instead.
New APIs:
- SearchEngine
public function defaultPrefixSearch( $search );
public function completionSearch( $search );
public function completionSearchWithVariants( $search );
Search engines should override:
protected function completionSearchBackend( $search );
Bug: T121430
Change-Id: Ie78649591dff94d21b72fad8e4e5eab010a461df
