Web Animations CSS: Rename SVG property interpolation tests to use 'svg-' prefix

BUG=257591
R=noel

Review URL: https://codereview.chromium.org/26627003

git-svn-id: svn://svn.chromium.org/blink/trunk@159229 bbb929c8-8fbe-4397-9dbb-9b2b20218538