The bison grammar for @supports should return 0 in case of an error
https://bugs.webkit.org/show_bug.cgi?id=115402

Reviewed by Darin Adler.

Back ported from https://chromium.googlesource.com/chromium/blink/+/74399c27c8b93286bae03a1d6371735935b34d85.

Source/WebCore:

Test: css3/supports-crash.html

* css/CSSGrammar.y.in:

LayoutTests:

* css3/supports-crash-expected.txt: Added.
* css3/supports-crash.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149376 268f45cc-cd09-0410-ab3c-d52691b4dbfc