Shift cookie system callbacks to OnceCallback to impedance match mojo.

chrome/browser/browsing_data/browsing_data_cookie_helper.cc

Index: chrome/browser/browsing_data/browsing_data_cookie_helper.cc
diff --git a/chrome/browser/browsing_data/browsing_data_cookie_helper.cc b/chrome/browser/browsing_data/browsing_data_cookie_helper.cc
index 0ae5e6aa6eef5c748d8373896d70de56b4e608cd..40d9dc8558d2f7988323e1c646b8bcd4994ea4cc 100644
--- a/chrome/browser/browsing_data/browsing_data_cookie_helper.cc
+++ b/chrome/browser/browsing_data/browsing_data_cookie_helper.cc
@@ -128,9 +128,8 @@ size_t CannedBrowsingDataCookieHelper::GetCookieCount() const {
   return count;
 }
 
-
 void CannedBrowsingDataCookieHelper::StartFetching(
-    const net::CookieStore::GetCookieListCallback& callback) {
+    const FetchCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   net::CookieList cookie_list;
   for (const auto& pair : origin_cookie_set_map_) {