Introduce toSVGRectElement(), use it
https://bugs.webkit.org/show_bug.cgi?id=119126

Reviewed by Andreas Kling.

As a step to change static_cast with toSVGXXX, static_cast<SVGRectElement*> can
be changed with toSVGRectElement().

No new tests, no behavior change.

* rendering/svg/RenderSVGRect.cpp:
(WebCore::RenderSVGRect::updateShapeFromElement):
* rendering/svg/SVGPathData.cpp:
(WebCore::updatePathFromRectElement):
* rendering/svg/SVGRenderTreeAsText.cpp:
(WebCore::operator<<):
* svg/SVGRectElement.h:
(WebCore::toSVGRectElement):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@153398 268f45cc-cd09-0410-ab3c-d52691b4dbfc