Move SVG inline flow box paint code to SVGInlineFlowBoxPainter

This patch moves the SVG inline flow box paint code to
SVGInlineFlowBoxPainter. This is a straight code move with no changes.

BUG=412088

Review URL: https://codereview.chromium.org/671943004

git-svn-id: svn://svn.chromium.org/blink/trunk@184219 bbb929c8-8fbe-4397-9dbb-9b2b20218538