Remove unused animation code after SVG prop migration

After the migration to the new SVG property implementation, some unused
functions were left. This patch removes the remainder of the unused
functions.

Review URL: https://codereview.chromium.org/208523005

git-svn-id: svn://svn.chromium.org/blink/trunk@169828 bbb929c8-8fbe-4397-9dbb-9b2b20218538