UseCounter: Assign new value to SVGAnimationElement.

We should not recycle unused enum value. Counter data should not depend on
Chrome version.

BUG=
R=isherman@chromium.org, pdr@chromium.org

Review URL: https://codereview.chromium.org/20626002

git-svn-id: svn://svn.chromium.org/blink/trunk@154966 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-rebaseline for r154918

http://src.chromium.org/viewvc/blink?view=revision&revision=154918

BUG=263879
TBR=eae@chromium.org

Review URL: https://codereview.chromium.org/20630003

git-svn-id: svn://svn.chromium.org/blink/trunk@154967 bbb929c8-8fbe-4397-9dbb-9b2b20218538