Add bindings tests coverage for reflected attributes with a SVG animated type

Add bindings tests coverage for reflected attributes with a SVG animated type.
We need to make sure getAttribute is used instead of fastGetAttribute.

R=haraken
BUG=328619

Review URL: https://codereview.chromium.org/105543004

git-svn-id: svn://svn.chromium.org/blink/trunk@163909 bbb929c8-8fbe-4397-9dbb-9b2b20218538