title: Still getting 'Symbol' is undefined' error even after adding babel-polyfill in my webpack
body: <p><a href="https://babeljs.io/docs/usage/polyfill/#usage-in-browser" rel="nofollow noreferrer">https://babeljs.io/docs/usage/polyfill/#usage-in-browser</a></p>
  
  <p>I did not understand the lines on the documentation page under:</p>
  
  <blockquote>
    <p>Usage in Browser heading</p>
  </blockquote>
  
  <p>can someone help me with what else is required:</p>
  
  <p>Below are my code snippets:</p>
  
  <p>I'm using storybook as a boilerplate:</p>
  
  <pre><code>webpack.config.js file:
  
  entry: [
      'babel-polyfill',
      require.resolve('react-dev-utils/webpackHotDevClient'),
      paths.appIndexJs
  ]
  
  index.js file:
  
  import 'babel-polyfill';
  import React from 'react';
  </code></pre>
  
  <p>Is there some other files also where I need to add <code>babel-polyfill</code> related code.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>require('babel-polyfill');
  var path = require('path');
  var autoprefixer = require('autoprefixer');
  var webpack = require('webpack');
  var HtmlWebpackPlugin = require('html-webpack-plugin');
  var CaseSensitivePathsPlugin = require('case-sensitive-paths-webpack-plugin');
  var InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
  var WatchMissingNodeModulesPlugin = require('react-dev-utils/WatchMissingNodeModulesPlugin');
  var getClientEnvironment = require('./env');
  var paths = require('./paths');
  var publicPath = '/';
  var publicUrl = '';
  var env = getClientEnvironment(publicUrl);
  module.exports = {
      devtool: 'cheap-module-source-map',
      entry: ['babel-polyfill',
          require.resolve('react-dev-utils/webpackHotDevClient'),
          require.resolve('./polyfills'),
          paths.appIndexJs
      ],
      output: {
          path: paths.appBuild,
          pathinfo: true,
          filename: 'static/js/bundle.js',
          publicPath: publicPath
      },
      resolve: {
          fallback: paths.nodePaths,
          extensions: ['.js', '.json', '.jsx', ''],
          alias: {
              'react-native': 'react-native-web'
          }
      },
      module: {
          // First, run the linter.
          // It's important to do this before Babel processes the JS.
          preLoaders: [{
              test: /\.(js|jsx)$/,
              loader: 'eslint',
              include: paths.appSrc,
          }],
          loaders: [{
                  exclude: [/\.html$/, /\.(js|jsx)$/, /\.css$/, /\.json$/],
                  loader: 'url',
                  query: {
                      limit: 10000,
                      name: 'static/media/[name].[hash:8].[ext]'
                  }
              },
              // Process JS with Babel.
              {
                  test: /\.(js|jsx)$/,
                  include: paths.appSrc,
                  loader: 'babel',
                  query: {
                      cacheDirectory: true
                  }
              }, {
                  test: /\.css$/,
                  loader: 'style!css?importLoaders=1!postcss'
              }, {
                  test: /\.json$/,
                  loader: 'json'
              }
          ]
      },
      // We use PostCSS for autoprefixing only.
      postcss: function() {
          return [
              autoprefixer({
                  browsers: ['&gt;1%', 'last 4 versions', 'Firefox ESR', 'not ie &lt; 9', // React doesn't support IE8 anyway
                  ]
              }),
          ];
      },
      plugins: [
          new InterpolateHtmlPlugin({
              PUBLIC_URL: publicUrl
          }),
          new HtmlWebpackPlugin({
              inject: true,
              template: paths.appHtml,
          }),
          new webpack.DefinePlugin(env),
          new webpack.HotModuleReplacementPlugin(),
          new CaseSensitivePathsPlugin(),
          new WatchMissingNodeModulesPlugin(paths.appNodeModules)
      ],
      node: {
          fs: 'empty',
          net: 'empty',
          tls: 'empty'
      }
  };</code></pre>
  </div>
  </div>
  </p>