Created attachment 312428 [details]
Symbol CSS Animation Test Case
CSS animations are not run for elements inside <symbol> SVG elements.
The attached 'Symbol CSS Animation Test Case' shows three rectangles. The red ones are symbols and the green one is not. Only the green one is rotating. I would expect to see all three rectangles rotating.
Chrome and Firefox show all three rectangles rotating.
Tested on Safari Technology Preview Release 32 (Safari 11.0, WebKit 12604.1.23.0.4) and Safari 10.1.1.