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

chrome/test/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/common/features.gni")
@@ skipping 2957 matching lines @@
     "../browser/android/data_usage/external_data_use_observer_unittest.cc",
     "../browser/android/data_usage/external_data_use_reporter_unittest.cc",
     "../browser/android/data_usage/tab_data_use_entry_unittest.cc",
     "../browser/android/digital_asset_links/digital_asset_links_handler_unittest.cc",
     "../browser/android/download/download_manager_service_unittest.cc",
     "../browser/android/history_report/data_observer_unittest.cc",
     "../browser/android/history_report/delta_file_backend_leveldb_unittest.cc",
     "../browser/android/history_report/delta_file_commons_unittest.cc",
     "../browser/android/history_report/usage_reports_buffer_backend_unittest.cc",
     "../browser/android/locale/special_locale_handler_unittest.cc",
+    "../browser/webauth/authenticator_web_contents_manager_unittest.cc",
 
     # TODO(newt): move this to test_support_unit?
     "../browser/android/chrome_backup_agent_unittest.cc",
     "../browser/android/favicon_helper_unittest.cc",
     "../browser/android/mock_location_settings.cc",
     "../browser/android/mock_location_settings.h",
     "../browser/android/net/external_estimate_provider_android_unittest.cc",
     "../browser/android/physical_web/eddystone_encoder_bridge_unittest.cc",
     "../browser/android/physical_web/physical_web_data_source_android_unittest.cc",
     "../browser/android/preferences/pref_service_bridge_unittest.cc",
@@ skipping 2187 matching lines @@
 }
 
 if (is_win) {
   loadable_module("conflicts_dll") {
     testonly = true
     sources = [
       "conflicts/conflicts_dll.cc",
     ]
   }
 }