Delete the NotificationActionIcons flag.

third_party/WebKit/Source/modules/notifications/NotificationAction.idl

 // Copyright 2015 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.
 
 // https://notifications.spec.whatwg.org/#dictdef-notificationaction
 
 [RuntimeEnabled=NotificationInlineReplies] enum NotificationActionType {
     "button",
     "text"
 };
 
 dictionary NotificationAction {
     [RuntimeEnabled=NotificationInlineReplies] NotificationActionType type = "button";
     required DOMString action;
     required DOMString title;
-    [RuntimeEnabled=NotificationActionIcons] USVString icon;
+    USVString icon;
     [RuntimeEnabled=NotificationInlineReplies] DOMString? placeholder = null;
 };