In the given test-case, the expected rendering would be "foobar foo" (this is how Opera renders it), instead it is rendered as "foofoo". In appears as if all but the first child of the run-in element is hidden and the content following is floated left.
Created attachment 55943 [details] Proposed Patch
Committed r59357: <http://trac.webkit.org/changeset/59357>
<rdar://problem/8707957>