1. @DomName('FontFaceSet.add')
  2. @DocsEditable()
  3. @Experimental()
void add(FontFace fontFace)

Source 

@DomName('FontFaceSet.add')
@DocsEditable()
@Experimental() // untriaged
void add(FontFace fontFace) =>
    _blink.BlinkFontFaceSet.instance.add_Callback_1_(this, fontFace);