Add layout test to validate the SVG2 inheritance model

Add layout test to validate the SVG2 inheritance model as per:
http://www.w3.org/TR/2013/WD-SVG2-20130618/

BUG=231536

Review URL: https://chromiumcodereview.appspot.com/20739003

git-svn-id: svn://svn.chromium.org/blink/trunk@155431 bbb929c8-8fbe-4397-9dbb-9b2b20218538