Add the Mojo implementation of authenticator.mojom's MakeCredential.

content/test/BUILD.gn

Index: content/test/BUILD.gn
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index d1855cb78d6ebdefb5e89a01adbe1da01186529c..bd4bf797882a671465f9c29795516e55e7f7618f 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -45,6 +45,8 @@ static_library("test_support") {
     "../browser/service_worker/embedded_worker_test_helper.h",
     "../browser/service_worker/service_worker_test_utils.cc",
     "../browser/service_worker/service_worker_test_utils.h",
+    "../browser/webauth/authenticator_impl.cc",
+    "../browser/webauth/authenticator_impl.h",

[jochen (gone - plz use gerrit), 2017/06/29 18:50:34]

no need to depend on the files here

     "../public/test/background_sync_test_util.cc",
     "../public/test/background_sync_test_util.h",
     "../public/test/browser_side_navigation_test_utils.cc",
@@ -1348,6 +1350,7 @@ test("content_unittests") {
     "../browser/web_contents/web_contents_view_mac_unittest.mm",
     "../browser/web_contents/web_drag_dest_mac_unittest.mm",
     "../browser/web_contents/web_drag_source_mac_unittest.mm",
+    "../browser/webauth/authenticator_impl_unittest.cc",
     "../browser/websockets/websocket_manager_unittest.cc",
     "../browser/webui/i18n_source_stream_unittest.cc",
     "../browser/webui/url_data_manager_backend_unittest.cc",