old_contents: import document
  
  pre = document.getElementById('edoutput')
  pre.innerHTML = '''
  <button onclick="var a=new XMLHttpRequest();a.open('GET','https://raw.githubusercontent.com/Zirientis/skulpt-canvas/master/core.js', false);a.send();console.log(a.response);">Run</button>
  <span id="evaltext" style="display:none">
  </span>
  '''
  
  # Put Python<->JS class here.
  class FakeCanvas:
      def fillRect(self, x, y, width, height):
          pass
      
  
new_contents: import document
  
  pre = document.getElementById('edoutput')
  pre.innerHTML = '''
  <button onclick="var a=new XMLHttpRequest();a.open('GET','https://raw.githubusercontent.com/Zirientis/skulpt-canvas/master/core.js', false);a.send();eval(a.response);">Run</button>
  <span id="evaltext" style="display:none">
  </span>
  '''
  
  # Put Python<->JS class here.
  class FakeCanvas:
      def fillRect(self, x, y, width, height):
          pass
      
  
subject: Make the terrible demo actually eval() the XHR.