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

third_party/WebKit/public/BUILD.gn

Index: third_party/WebKit/public/BUILD.gn
diff --git a/third_party/WebKit/public/BUILD.gn b/third_party/WebKit/public/BUILD.gn
index 1cfc957b372ae432ef464f6d0c04c459fb1bc73a..5d6fce171d3430fc421fc7033dd520aacbc283a0 100644
--- a/third_party/WebKit/public/BUILD.gn
+++ b/third_party/WebKit/public/BUILD.gn
@@ -707,6 +707,7 @@ grit("image_resources") {
 mojom("mojo_bindings") {
   visibility = [
     "//components/payments/content/*",
+    "//components/webauth/*",
     "//content/*",
   ]
   visibility_blink = [
@@ -736,6 +737,7 @@ mojom("mojo_bindings") {
     "platform/modules/sensitive_input_visibility/sensitive_input_visibility_service.mojom",
     "platform/modules/serviceworker/service_worker_event_status.mojom",
     "platform/modules/serviceworker/service_worker_stream_handle.mojom",
+    "platform/modules/webauth/authenticator.mojom",
     "platform/modules/websockets/websocket.mojom",
     "platform/referrer.mojom",
     "platform/site_engagement.mojom",