<script src> in custom element puts methods in global scope

Currently, foo() is not seen in global scope (index.html that uses x-element). Good! 
But bar() is from app.js. Not x-element.html contains <script='app.js'></script>. 

app.js:
function bar() {}

x-element.html:
<element>
  <template>
  <script='app.js'></script>
    ...
  </template>
  <script>
    function foo() { }
  </script>
</element>
