Add browser test for notification action icons.

content/child/runtime_features.cc

Index: content/child/runtime_features.cc
diff --git a/content/child/runtime_features.cc b/content/child/runtime_features.cc
index 760ed983caa888b57cf170c1b39ff0be2bfdb88d..1ad1981e747d47b6a7888bd614a4e2d5be45e928 100644
--- a/content/child/runtime_features.cc
+++ b/content/child/runtime_features.cc
@@ -93,6 +93,9 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
     WebRuntimeFeatures::enablePushMessaging(false);
   }
 
+  if (command_line.HasSwitch(switches::kEnableNotificationActionIcons))
+    WebRuntimeFeatures::enableNotificationActionIcons(true);
+
   if (command_line.HasSwitch(switches::kDisableSharedWorkers))
     WebRuntimeFeatures::enableSharedWorker(false);