Introduce isSVGFontElement() and isSVGImageElement(), use them
https://bugs.webkit.org/show_bug.cgi?id=118504

Reviewed by Benjamin Poulain.

Let's use isFoo() to enhance readibility in svg element classes along with html's.

No new tests, there is no behavior changes.

* loader/cache/CachedFont.cpp:
(WebCore::CachedFont::getSVGFontById):
* rendering/HitTestResult.cpp:
(WebCore::HitTestResult::absoluteImageURL):
* svg/SVGAnimateMotionElement.cpp:
(WebCore::SVGAnimateMotionElement::hasValidAttributeType):
* svg/SVGElement.cpp:
(WebCore::SVGElement::viewportElement):
* svg/SVGFontElement.cpp:
(WebCore::SVGFontElement::SVGFontElement):
* svg/SVGFontElement.h:
(WebCore::toSVGFontElement):
(WebCore::isSVGFontElement):
* svg/SVGFontFaceElement.cpp:
(WebCore::SVGFontFaceElement::associatedFontElement):
(WebCore::SVGFontFaceElement::rebuildFontFace):
* svg/SVGGlyphElement.cpp:
(WebCore::SVGGlyphElement::invalidateGlyphCache):
* svg/SVGHKernElement.cpp:
(WebCore::SVGHKernElement::insertedInto):
(WebCore::SVGHKernElement::removedFrom):
* svg/SVGImageElement.cpp:
(WebCore::SVGImageElement::SVGImageElement):
* svg/SVGImageElement.h:
(WebCore::toSVGImageElement):
(WebCore::isSVGImageElement):
* svg/SVGLocatable.cpp:
(WebCore::isViewportElement):
* svg/SVGVKernElement.cpp:
(WebCore::SVGVKernElement::insertedInto):
(WebCore::SVGVKernElement::removedFrom):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@152524 268f45cc-cd09-0410-ab3c-d52691b4dbfc