window.navigation needs to be [Replaceable]

See https://bugs.webkit.org/show_bug.cgi?id=297721 for context.

Author: annevk

source

@@ -95084,7 +95084,7 @@ interface <dfn interface>Window</dfn> : <span>EventTarget</span> {
   attribute DOMString <span data-x="dom-name">name</span>; <!-- not [Replaceable] per WebKit and IE8 -->
   [PutForwards=<span data-x="dom-location-href">href</span>, <span>LegacyUnforgeable</span>] readonly attribute <span>Location</span> <span data-x="dom-location">location</span>;
   readonly attribute <span>History</span> <span data-x="dom-history">history</span>;
-  readonly attribute <span>Navigation</span> <span data-x="dom-navigation">navigation</span>;
+  [Replaceable] readonly attribute <span>Navigation</span> <span data-x="dom-navigation">navigation</span>;
   readonly attribute <span>CustomElementRegistry</span> <span data-x="dom-window-customElements">customElements</span>;
   [Replaceable] readonly attribute <span>BarProp</span> <span data-x="dom-window-locationbar">locationbar</span>;
   [Replaceable] readonly attribute <span>BarProp</span> <span data-x="dom-window-menubar">menubar</span>;