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

content/public/app/mojo/content_browser_manifest.json

 {
   "name": "content_browser",
   "display_name": "Content (browser process)",
   "interface_provider_specs": {
     "service_manager:connector": {
       "provides": {
         "gpu": [
           "content::mojom::FieldTrialRecorder",
           "media::mojom::AndroidOverlayProvider"
         ],
@@ skipping 103 matching lines @@
           "media::mojom::ImageCapture",
           "media::mojom::InterfaceFactory",
           "media::mojom::RemoterFactory",
           "media::mojom::Renderer",
           "mojom::MediaDevicesDispatcherHost",
           "payments::mojom::PaymentRequest",
           "resource_coordinator::mojom::CoordinationUnit",
           "shape_detection::mojom::BarcodeDetection",
           "shape_detection::mojom::FaceDetectionProvider",
           "shape_detection::mojom::TextDetection",
-          "ui::mojom::Gpu"
+          "ui::mojom::Gpu",
+          "webauth::mojom::Authenticator"
         ]
       },
       "requires": {
         "content_renderer": [ "browser" ]
       }
     }
   }
 }