For headless, we can't show a UI warning for bad certificates as chrome does. Instead, we should investigate exposing certificate errors as events through DevTools and controlling what action to take through a DevTools command.
FYI, currently such errors are handled in SSLManager::OnCertErrorInternal, which delegates to ContentBrowserClient::AllowCertificateError.
Comment 1 by skyos...@chromium.org
, Dec 5 2016