Slightly improve performance of CSSStyleApplyProperty handler lookup.

Slightly improve performance of CSSStyleApplyProperty handler lookup.
https://bugs.webkit.org/show_bug.cgi?id=68868

Reviewed by Eric Seidel.

No new tests as no functionality changed.

* css/CSSStyleApplyProperty.h:
(WebCore::CSSStyleApplyProperty::propertyHandler):
Make propertyHandler() public and remove redirecting functions.
* css/CSSStyleSelector.cpp:
(WebCore::CSSStyleSelector::applyProperty):
Perform property handler lookup once and reuse the result.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96168 268f45cc-cd09-0410-ab3c-d52691b4dbfc