Removed unused method from |AutofillManager|.

Change-Id: I62a99216ab1d303c5a4e84a9ee83e5ec576bef29
Bug: 1007974
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1827284
Commit-Queue: Matthias Körber <koerber@google.com>
Commit-Queue: Vadym Doroshenko <dvadym@chromium.org>
Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700214}

components/autofill/core/browser/autofill_manager.h

@@ -311,9 +311,6 @@ class AutofillManager : public AutofillHandler,
     return form_interactions_ukm_logger_.get();
   }
 
-  // Exposed for testing.
-  AutofillExternalDelegate* external_delegate() { return external_delegate_; }
-
   // Exposed for testing.
   void set_download_manager(AutofillDownloadManager* manager) {
     download_manager_.reset(manager);