Make more computed style helpers return values by PassRef.
<https://webkit.org/b/125923>

Tighten yet another handful of CSS computed style helper functions
to return their CSSValues by PassRef where we never return null.

Reviewed by Antti Koivisto.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@160765 268f45cc-cd09-0410-ab3c-d52691b4dbfc
CSS: Null-pointer dereference with negative 'orphans' value.
https://bugs.webkit.org/show_bug.cgi?id=125924

Patch by Dániel Bátyai <dbatyai.u-szeged@partner.samsung.com> on 2013-12-18
Reviewed by Andreas Kling.

Source/WebCore:

orphans and widows should be positive integer.

spec link:
http://www.w3.org/TR/CSS2/page.html#propdef-orphans

Backported from Blink: https://codereview.chromium.org/108663009

Test: fast/css/negative-orphans-crash.html

* css/CSSParser.cpp:
(WebCore::CSSParser::parseValue):

LayoutTests:

Test with negative orphans value.

* fast/css/negative-orphans-crash-expected.txt: Added.
* fast/css/negative-orphans-crash.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@160766 268f45cc-cd09-0410-ab3c-d52691b4dbfc