https://bugs.webkit.org/show_bug.cgi?id=118960

Reviewed by Allan Sandfeld Jensen.

Though there is toSVGPathElement(), some files still use static_cast<SVGPathElement*>.
To remove all static_cast<> use, we need to change argument from SVGElement to Element.

Merge from https://src.chromium.org/viewvc/blink?view=rev&revision=154621

No new tests, no behavior change.

* rendering/svg/RenderSVGTextPath.cpp:
(WebCore::RenderSVGTextPath::layoutPath):
* rendering/svg/SVGPathData.cpp:
(WebCore::updatePathFromPathElement):
* rendering/svg/SVGRenderTreeAsText.cpp:
(WebCore::operator<<):
* svg/SVGMPathElement.cpp:
(WebCore::SVGMPathElement::pathElement):
* svg/SVGPathElement.h:
(WebCore::toSVGPathElement):
* svg/SVGPathSegList.cpp:
(WebCore::SVGPathSegList::commitChange):
* svg/properties/SVGAnimatedPathSegListPropertyTearOff.h:
(WebCore::SVGAnimatedPathSegListPropertyTearOff::animValDidChange):
* svg/properties/SVGPathSegListPropertyTearOff.cpp:
(WebCore::SVGPathSegListPropertyTearOff::contextElement):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@152962 268f45cc-cd09-0410-ab3c-d52691b4dbfc