Move paint code from RenderSVGText to SVGTextPainter

This patch moves the RenderSVGText paint code into the new SVGTextPainter.
This is a straight code move and the only change that was need was to
expose localToParentTransform as public on RenderSVGText.

BUG=412088

Review URL: https://codereview.chromium.org/599283002

git-svn-id: svn://svn.chromium.org/blink/trunk@182642 bbb929c8-8fbe-4397-9dbb-9b2b20218538