Search for |searchText|. |forward| indicates whether to search forward or backward within the page. |matchCase| indicates whether the search should be case-sensitive. |findNext| indicates whether this is the first request or a follow-up. The search will be restarted if |searchText| or |matchCase| change. The search will be stopped if |searchText| is NULL. The cef_find_handler_t instance, if any, returned via