I have tried to modify the logoutbutton widget.
Apparently, the original one can't change the 'height' property.
So, I copy some parts of the button widget's code.
But it seems that logoutbutton can't appear in runtime.
'description': 'height of widget',
// 'isEditable': false
I've changed the height property, and it seems that runtime.js is mostly same as the button widget.