Add DiscoveryNetworkMonitor implementation

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index 9072029d2cfffc7578cb9b50312c2b9e6e699022..84e562d879ca6f1c9d2da1fdc62eee90b50f6d11 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -3213,6 +3213,8 @@ test("unit_tests") {
     "../browser/metrics/thread_watcher_unittest.cc",
     "../browser/mod_pagespeed/mod_pagespeed_metrics_unittest.cc",
     "../browser/net/chrome_network_delegate_unittest.cc",
+    "../browser/net/discovery_network_list_unittest.cc",
+    "../browser/net/discovery_network_monitor_unittest.cc",
     "../browser/net/dns_probe_runner_unittest.cc",
     "../browser/net/dns_probe_service_unittest.cc",
     "../browser/net/file_downloader_unittest.cc",
@@ -4510,9 +4512,8 @@ test("unit_tests") {
       "//third_party/ocmock",
     ]
 
-    sources += [
-      "../browser/ui/cocoa/applescript/apple_event_util_unittest.mm",
-    ]
+    sources +=
+        [ "../browser/ui/cocoa/applescript/apple_event_util_unittest.mm" ]
 
     if (mac_views_browser) {
       # TODO(tapted): Add chrome_unit_tests_views_non_mac_sources.