title: BabelHelpers is not defined using Polymer
body: <p>I'm using Polymer and its build process. The bundled files are generated throughmy polymer.json file.</p>
  
  <p>I'm not explicitely using Babel, I've just seen it's used by "paper-autocomplete".</p>
  
  <p>When going to the website, I have a js error stating the BabelHelpers is not defined.</p>
  
  <ul>
  <li>When I use MAJ+F5, it works ! </li>
  <li>When I use F5, it doesn't work
  (BabelHelpers is not defined)</li>
  </ul>
  
  <p>When running it locally it works fine. When I deploy it to my server, I face this issue.</p>
  
  <p>I'm running it as a standalone Java application as it has a Spring backend.
  The website as multiple entry points, it works fine for all other ones.</p>
  
  <p><strong>The stacktrace :</strong> </p>
  
  <p><a href="https://i.stack.imgur.com/w2v29.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/w2v29.png" alt="BabelHelpers"></a></p>
  
  <p><strong>Command :</strong> </p>
  
  <pre><code>polymer build --js-minify --css-minify --html-minify
  </code></pre>
  
  <p><strong>The polymer.json file</strong> </p>
  
  <pre><code>{
    "entrypoint": "pt.html",
    "builds": [{
        "bundle": true,
        "js": {"compile": true, "minify": true},
        "css": {"minify": true},
        "html": {"minify": false},
        "addServiceWorker": true 
      }],
    "shell": "resources/elements-platform.html",
    "fragments": [
      "resources/html/lazy-resources.html",
      "resources/html/ym-dashboard.html",
      "resources/html/ym-partners.html",
      "resources/html/ym-favorite.html",
      "resources/html/ym-agenda.html",
      "resources/html/ym-todos.html",
      "resources/html/ym-profile.html",
      "resources/html/ym-messages.html",
      "resources/html/shop-list.html",
      "resources/html/shop-detail.html"
    ],
    "sources": [
     "resources/src/**/*",
     "resources/css/**/*",
     "resources/data/**/*",
     "resources/images/**/*",
     "resources/img/**/*",
     "resources/js/*",
     "resources/js/cal/*",
     "resources/js/countdown/*",
     "resources/bower.json"
    ],
    "extraDependencies": [
      "resources/bower_components/webcomponentsjs/webcomponents-lite.min.js"
    ]
  }
  </code></pre>