1. DomName('SVGLengthList.insertItemBefore')
  2. DocsEditable()
Length insertItemBefore(Length newItem, int index)

Source 

@DomName('SVGLengthList.insertItemBefore')
@DocsEditable()
Length insertItemBefore(Length newItem, int index) => _blink.BlinkSVGLengthList.instance.insertItemBefore_Callback_2_(this, newItem, index);