https://bugs.webkit.org/show_bug.cgi?id=64763

Reviewed by Ojan Vafai.

No new tests because no change in functionality.

* css/CSSFlexValue.h:
(WebCore::CSSFlexValue::create):
(WebCore::CSSFlexValue::isFlexValue): Make it possible to tell if
    we're a flex value or not.  Will be needed when we're copying
    values to RenderStyle.
(WebCore::CSSFlexValue::positiveFlex): Use floats for positive and
    negative flex because in the render code, we use floats.
(WebCore::CSSFlexValue::negativeFlex): Add accessors for these since
    we'll need it when reading the flex values.
(WebCore::CSSFlexValue::preferredSize):
(WebCore::CSSFlexValue::CSSFlexValue):
* css/CSSParser.cpp:
(WebCore::CSSParser::parseValidPrimitive): Make the type more
    specific.
(WebCore::CSSParser::parseFlex):
* css/CSSParser.h:
* css/CSSValue.h:
(WebCore::CSSValue::isFlexValue):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@91268 268f45cc-cd09-0410-ab3c-d52691b4dbfc