anchor.diff:          LeafletMap.prototype = {
               constructor: LeafletMap,
               addTileLayer: function() {
  -                L.tileLayer('http://korona.geog.uni-heidelberg.de/tiles/roadsg/x={x}&y={y}&z={z}', {
  +                L.tileLayer('https://tiles.wmflabs.org/bw-mapnik/{z}/{x}/{y}.png', {
                       attribution: ''
                   }).addTo(this._map);
               },
  
positive.code:     <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
      <link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet">
      <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-material-design/0.5.9/css/bootstrap-material-design.min.css">
      <link rel="stylesheet" href="https://cdn.leafletjs.com/leaflet-0.7/leaflet.css" />
      <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css">
      <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/leaflet.draw/0.2.3/leaflet.draw.css">
      <link rel="stylesheet" href="/css/common.css">
  
negative.code:     <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.0/jquery.min.js"></script>
      <script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
      <script src="https://fezvrasta.github.io/bootstrap-material-design/dist/js/material.min.js"></script>
      <script src="https://cdnjs.cloudflare.com/ajax/libs/leaflet/0.7.0/leaflet.js"></script>
      <script src="https://cdnjs.cloudflare.com/ajax/libs/leaflet.draw/0.2.3/leaflet.draw.js"></script>
      <script>$.material.init();</script>
      <script>
  