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

chrome/browser/BUILD.gn

Index: chrome/browser/BUILD.gn
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 099ffb25aad053bf229ce1d87db700ff6d701295..c7289df7fe8db8aed3f80f38b4314aad20272e7c 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -1568,6 +1568,7 @@ split_static_library("browser") {
     "//components/visitedlink/common",
     "//components/web_cache/browser",
     "//components/web_resource",
+    "//components/webauth:webauth",
     "//components/webdata/common",
     "//components/webdata_services",
     "//components/zoom",
@@ -3719,6 +3720,14 @@ split_static_library("browser") {
     deps += [ "//components/payments/content" ]
   }
 
+  if (is_linux || is_win || is_mac) {
+    sources += [
+      "webauth/authenticator_web_contents_manager.cc",
+      "webauth/authenticator_web_contents_manager.h",
+    ]
+    deps += [ "//components/webauth:authenticator" ]
+  }
+
   if (is_linux || is_win) {
     sources += [
       "renderer_context_menu/spelling_options_submenu_observer.cc",