This CL refactors the animation AST code to make use of interfaces instead of classes. Given that interfaces are not persisted during runtime the removal of classes should nicely cut down on size for the animations-browser bundle.
-- before --
animations-browser.umd.js = 222kb
animations-browser.umd.min.js = 107kb
-- after --
animations-browser.umd.js = 213kb
animations-browser.umd.min.js = 102kb
PR Close#19539