The @keyframes parser was storing the keyframes name via
Token::to_string(), which keeps a string token in its quoted,
serialized form. That meant @keyframes "foo" was stored as
"\"foo\"" while animation-name: "foo" resolved to "foo",
and the two never matched.
Store the unquoted string or identifier value so the @keyframes name
and the animation-name reference compare on the same string.
e4800b2498