Use real ES2015 classes in tests for reflect shim. (...)
Use real ES2015 classes in tests for reflect shim. (...)

If the browser doesn't support ES2015, `polymer test` will compile the classes
out, but then native custom elements are also unsupported natively and these
suites will be skipped anyway.

webcomponents/polyfills,webcomponents/polyfills,webcomponents/polyfills