spec/fixtures/pages/zoom-factor.html (8 lines of code) (raw):
<html>
<body>
<script type="text/javascript" charset="utf-8">
const {ipcRenderer, webFrame} = require('electron')
ipcRenderer.send('webview-parent-zoom-level', webFrame.getZoomFactor(), webFrame.getZoomLevel())
</script>
</body>
</html>