Although I'm not 100% satisfied, this does do the job.
I'm now using a small bit of jQuery.
jQuery( document ).ready( function( $ ) {
$( '.btn' ).css( 'animation-name', function( index, value) {
return $( this ).attr('class').replace( / /g, ',' );
});
$( '.btn' ).css( '-webkit-animation-name', function( index, value) {
return $( this ).attr('class').replace( / /g, ',' );
});
});`