Add DiscoveryNetworkMonitor implementation

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 3022 matching lines @@
     "../browser/logging_chrome_unittest.cc",
     "../browser/mac/exception_processor_unittest.mm",
     "../browser/mac/keystone_glue_unittest.mm",
     "../browser/manifest/manifest_icon_downloader_unittest.cc",
     "../browser/manifest/manifest_icon_selector_unittest.cc",
     "../browser/media/android/router/media_router_android_unittest.cc",
     "../browser/media/cast_remoting_connector_unittest.cc",
     "../browser/media/midi_permission_context_unittest.cc",
     "../browser/media/router/browser_presentation_connection_proxy_unittest.cc",
     "../browser/media/router/create_presentation_connection_request_unittest.cc",
+    "../browser/media/router/discovery/discovery_network_list_unittest.cc",
+    "../browser/media/router/discovery/discovery_network_monitor_unittest.cc",
     "../browser/media/router/issue_manager_unittest.cc",
     "../browser/media/router/media_router_base_unittest.cc",
     "../browser/media/router/media_router_dialog_controller_unittest.cc",
     "../browser/media/router/media_router_factory_unittest.cc",
     "../browser/media/router/media_router_metrics_unittest.cc",
     "../browser/media/router/media_sinks_observer_unittest.cc",
     "../browser/media/router/offscreen_presentation_manager_factory_unittest.cc",
     "../browser/media/router/offscreen_presentation_manager_unittest.cc",
     "../browser/media/router/presentation_media_sinks_observer_unittest.cc",
     "../browser/media/router/presentation_request_unittest.cc",
@@ skipping 2004 matching lines @@
 }
 
 if (is_win) {
   loadable_module("conflicts_dll") {
     testonly = true
     sources = [
       "conflicts/conflicts_dll.cc",
     ]
   }
 }