Layout.isDefaultLayout ()
Helper function: is this layout the default in the current context?

Sourcecode in Layout/objectFunctions.js:
1:   function isDefaultLayout() {
2:      if (this.site && this.site.layout == this)
3:         return true;
4:      if (!this.site && root.sys_layout == this)
5:         return true;
6:      return false;
7:   }