How to collect sub frame's statistics with 'about:blank' src?

[sober1998]

When I load the url: fingerprintjs, I don't think I got the correct statistics. This page has a sub frame with src as 'about:blank', HTMLElement.offsetWidth and HTMLElement.offsetHeight are called in this sub frame, but I can't find those calls in the database. Sub frame is generated by javascript file in this web page. My fingerprinting.json is:

[
  "HTMLIFrameElement",
  "Date",
  "AudioParam",
  "DynamicsCompressorNode",
  "OscillatorNode",
  "MediaQueryList",
  "CanvasRenderingContext2D",
  "HTMLCanvasElement",
  {"HTMLElement": {
    "propertiesToInstrument": ["offsetWidth", "offsetHeight", "textContent", "appendChild"]
  }}
]

How can I collect the correct information under such circumstances？