Object getContext(String contextId, [ Map attributes ])

Source 

Object getContext(String contextId, [Map attributes]) {
  if (attributes != null) {
    return _blink.BlinkHTMLCanvasElement.instance.getContext_Callback_2_(
        this, contextId, convertDartToNative_Dictionary(attributes));
  }
  return _blink.BlinkHTMLCanvasElement.instance
      .getContext_Callback_1_(this, contextId);
}