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);