CSS 2.1 failure: at-import-009.htm fails

CSS 2.1 failure: at-import-009.htm fails
https://bugs.webkit.org/show_bug.cgi?id=82921

Source/WebCore:

Reviewed by Antti Koivisto.

This fixes at-import-009.htm only, the other tests already passed.

Tests: css2.1/20110323/at-import-001.htm
       css2.1/20110323/at-import-002.htm
       css2.1/20110323/at-import-003.htm
       css2.1/20110323/at-import-004.htm
       css2.1/20110323/at-import-005.htm
       css2.1/20110323/at-import-006.htm
       css2.1/20110323/at-import-007.htm
       css2.1/20110323/at-import-009.htm
       css2.1/20110323/at-import-010.htm
       css2.1/20110323/at-import-011.htm

* css/CSSGrammar.y: ignore empty '@media;' and '@charset;' declarations

LayoutTests:

Add the at-import-* tests from the CSS 2.1 suite. Skip at-import-008.htm
as it relies on a print media type to work.

Reviewed by Antti Koivisto.

* css2.1/20110323/at-import-001-expected.html: Added.
* css2.1/20110323/at-import-001.htm: Added.
* css2.1/20110323/at-import-002-expected.html: Added.
* css2.1/20110323/at-import-002.htm: Added.
* css2.1/20110323/at-import-003-expected.html: Added.
* css2.1/20110323/at-import-003.htm: Added.
* css2.1/20110323/at-import-004-expected.html: Added.
* css2.1/20110323/at-import-004.htm: Added.
* css2.1/20110323/at-import-005-expected.html: Added.
* css2.1/20110323/at-import-005.htm: Added.
* css2.1/20110323/at-import-006-expected.html: Added.
* css2.1/20110323/at-import-006.htm: Added.
* css2.1/20110323/at-import-007-expected.html: Added.
* css2.1/20110323/at-import-007.htm: Added.
* css2.1/20110323/at-import-009-expected.html: Added.
* css2.1/20110323/at-import-009.htm: Added.
* css2.1/20110323/at-import-010-expected.html: Added.
* css2.1/20110323/at-import-010.htm: Added.
* css2.1/20110323/at-import-011-expected.html: Added.
* css2.1/20110323/at-import-011.htm: Added.
* css2.1/20110323/support/at-import-001.css: Added.
* css2.1/20110323/support/at-import-002.css: Added.
* css2.1/20110323/support/at-import-004.css: Added.
* css2.1/20110323/support/at-import-005.css: Added.
* css2.1/20110323/support/at-import-006.css: Added.
* css2.1/20110323/support/at-import-007.css: Added.
* css2.1/20110323/support/import-green.css: Added.
* css2.1/20110323/support/import-red.css: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@113076 268f45cc-cd09-0410-ab3c-d52691b4dbfc