1. @DomName('SVGTextContentElement.getSubStringLength')
  2. @DocsEditable()
num getSubStringLength(int charnum, int nchars)

Source 

@DomName('SVGTextContentElement.getSubStringLength')
@DocsEditable()
num getSubStringLength(int charnum, int nchars) =>
    _blink.BlinkSVGTextContentElement.instance
        .getSubStringLength_Callback_2_(this, charnum, nchars);