Currently, a StyleRuleKeyframes instance is created in the empty alternative of "keyframes_rule", which makes use of the left recursion. This is inconsistent with the current approach of "floating" lists used when parsing sequences of other objects (selectors, rules in a block rule, etc.) and requires complex constructs to implement the sourcecode data extraction for keyframes rules.
Also, the current grammar does not allow the abrupt termination of a @-webkit-keyframes rule (i.e. a missing closing brace), which is required by http://www.w3.org/TR/CSS21/syndata.html#parsing-errors (see bug 89980, which treats the same issue about the @font-face rule).
Created attachment 149915 [details]
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Created attachment 149927 [details]
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Committed r121531: <http://trac.webkit.org/changeset/121531>