Factor SVGMarkerPainter into SVGShapePainter

SVGShapePainter is the only class to paint markers so the marker painter
class is all overhead. This patch moves the marker painter code into
SVGShapePainter.

BUG=412088

Review URL: https://codereview.chromium.org/693313003

git-svn-id: svn://svn.chromium.org/blink/trunk@184895 bbb929c8-8fbe-4397-9dbb-9b2b20218538