Babel 7 (#23966)

* use .babelrc.js, compile bundled/non-bundled with loose mode

* add back helper, exclude typeof transform

build/rollup.config.js

@@ -11,11 +11,9 @@ const plugins = [
   babel({
     exclude: 'node_modules/**', // only transpile our source code
     externalHelpersWhitelist: [ // include only required helpers
-      'typeof',
-      'classCallCheck',
+      'defineProperties',
       'createClass',
-      'inherits',
-      'possibleConstructorReturn'
+      'inheritsLoose'
     ]
   })
 ]