EPHY_GET_EMBED_FROM_EPHY_WEB_VIEW() fails on WebExtension views
For example ephy-web-view.c#process_terminated_cb()
calls EPHY_GET_EMBED_FROM_EPHY_WEB_VIEW()
which assumes that EphyEmbed
widget is always two parents up. This is no longer true now that WebExtensions embed views in other locations.
Either this macro needs to become a smarter function, WebExtensions shouldn't use EphyWebView, or we need to detect WebExtension views throughout.