Make the authentication service remember selected usernames.

services/authentication/BUILD.gn

Index: services/authentication/BUILD.gn
diff --git a/services/authentication/BUILD.gn b/services/authentication/BUILD.gn
index 72b61bcfc54a9cbd8d7340300da40d3094583589..88c72a6ebfce8699ecde9d48faf171c2615a285f 100644
--- a/services/authentication/BUILD.gn
+++ b/services/authentication/BUILD.gn
@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//mojo/public/tools/bindings/mojom.gni")
+
 if (is_android) {
   import("//services/android/rules.gni")
 
@@ -14,6 +16,7 @@ if (is_android) {
     mojo_main = "org.chromium.mojo.authentication.AuthenticationApp"
 
     deps = [
+      ":interfaces_java",
       "//mojo/public/interfaces/application:application_java",
       "//mojo/public/java:application",
       "//mojo/services/authentication/public/interfaces:interfaces_java",
@@ -21,4 +24,10 @@ if (is_android) {
       "//third_party/android_tools:google_play_services_default_java",
     ]
   }
+
+  mojom("interfaces") {
+    sources = [
+      "authentication_impl_db.mojom",
+    ]
+  }
 }