Implement SVGGeometryElement

Implement SVGGeometryElement as described in https://svgwg.org/svg2-draft/types.html#InterfaceSVGGeometryElement

Use existing nodeAtPoint functionality from RenderSVGShape to implement the isPointInFill/Stroke methods of the interface.

Because of this feature update svg2-inheritance.html and add tests for it in svg-ellipse.xhtml.

TESTS=svg/dom/svg2-inheritance.html, svg/hittest/svg-ellipse.xhtml
BUG=315802

Review URL: https://codereview.chromium.org/62943002

git-svn-id: svn://svn.chromium.org/blink/trunk@161828 bbb929c8-8fbe-4397-9dbb-9b2b20218538