1. DomName('Document.getElementsByTagName')
  2. DocsEditable()
List<Node> getElementsByTagName(String localName)

Source 

@DomName('Document.getElementsByTagName')
@DocsEditable()
List<Node> getElementsByTagName(String localName) => wrap_jso(_blink.BlinkDocument.instance.getElementsByTagName_Callback_1_(unwrap_jso(this), localName));