fix: crash when navigating from a page with webview that has inherited zoom level (#24757)

* fix: cleanup webview zoom level observers on navigation

* add spec

* webview should be on same partition

* wait for webview to finish loading

shell/browser/api/electron_api_web_contents.cc

@@ -1413,6 +1413,11 @@ bool WebContents::OnMessageReceived(const IPC::Message& message) {
 // we need to make sure the api::WebContents is also deleted.
 // For #4, the WebContents will be destroyed by embedder.
 void WebContents::WebContentsDestroyed() {
+  // Give chance for guest delegate to cleanup its observers
+  // since the native class is only destroyed in the next tick.
+  if (guest_delegate_)
+    guest_delegate_->WillDestroy();
+
   // Cleanup relationships with other parts.
   RemoveFromWeakMap();