BackgroundFetchRegistration.abort() should return a Promise.

content/browser/background_fetch/background_fetch_service_impl.h

Index: content/browser/background_fetch/background_fetch_service_impl.h
diff --git a/content/browser/background_fetch/background_fetch_service_impl.h b/content/browser/background_fetch/background_fetch_service_impl.h
index ffc29862fdae9404bebaa6f8dd3167dc47b1ede5..3f03b9cec3040cbacd5920b8b67d82089283b10b 100644
--- a/content/browser/background_fetch/background_fetch_service_impl.h
+++ b/content/browser/background_fetch/background_fetch_service_impl.h
@@ -35,7 +35,8 @@ class BackgroundFetchServiceImpl : public blink::mojom::BackgroundFetchService {
                 const std::string& title,
                 const UpdateUICallback& callback) override;
   void Abort(int64_t service_worker_registration_id,
-             const std::string& tag) override;
+             const std::string& tag,
+             const AbortCallback& callback) override;
   void GetRegistration(int64_t service_worker_registration_id,
                        const std::string& tag,
                        const GetRegistrationCallback& callback) override;