[Cast+Zenith] Call Layout() after adding new cast devices

Bug: b/161610050, 1107162
Change-Id: I3e6ee484b06b0e35a3a5fda55aba12e867f08d8a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462486Reviewed-by: Tommy Steimel <steimel@chromium.org>
Commit-Queue: Muyao Xu <muyaoxu@google.com>
Cr-Commit-Position: refs/heads/master@{#815799}

chrome/browser/ui/views/global_media_controls/media_notification_device_selector_view.cc

@@ -361,6 +361,8 @@ void MediaNotificationDeviceSelectorView::OnModelUpdated(
     device_entry_ui_map_[device_entry_view->tag()] = device_entry_view.get();
     device_entry_views_container_->AddChildView(std::move(device_entry_view));
   }
+  device_entry_views_container_->Layout();
+
   UpdateVisibility();
 }