Created attachment 343755 [details]
testcase (requires Ahem)
In light of discussions for extending the format() descriptor to handle features (e.g. colors, variations) within a particular font format, the CSSWG recently resolved to update the parsing rules for @font-face's src descriptor to be more forwards-compatible, using Media Queries style parsing rules to split on top-level commas, and discard only the invalid items in the src list rather than throwing out the entire descriptor.
I think this is an important change to implement even before the new features are implemented, as it means WebKit will be forwards-compatible with content authored using new format() features, whatever they end up being.