[css-fonts] Some WPT font parsing tests fail due to insecure operations

[svgeesus]

web-platform-tests/wpt#9103

See https://test.csswg.org/harness/details/css-fonts-3_dev/test_font_family_parsing/

and run this test (with automatic submission off, so you can see the failures)
https://test.csswg.org/harness/test/css-fonts-3_dev/single/test_font_family_parsing/

[svgeesus]

Closing because unable to reproduce; no longer seeing the "insecure operation" warning in the test

[svgeesus]

aaand re-opening because here it is again in Firefox nightly 60.0a1 (2018-01-23) (64-bit)

[svgeesus]

This turned out to be a transient issue and is now fixed in Firefox 61. Closing.