OpenLayers GeoJSON as BaseLayer

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/openlayers/2.13.1/OpenLayers.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/openlayers/2.13.1/theme/default/style.css">
<script src="https://rawgit.com/anonymous/f9f64d27fc5682574c90/raw/e9e8eaa0089ed994b014d17f7637744601278dfd/world_0.js"></script>
<body onload="Initialize()">OpenLayers GeoJSON-Layer as BaseLayer
    <br />
    <div id="mapDiv"></div>
</body>

CSS

#mapDiv {
    height:400px;
    width:600px;
    border: 1px solid red;
}

JavaScript

var lon = 5;
var lat = 40;
var zoom = 5;
var map;

function Initialize() {

    // Map
    map = new OpenLayers.Map('mapDiv', {
        controls: [
        new OpenLayers.Control.Navigation(),
        new OpenLayers.Control.PanZoomBar(),
        new OpenLayers.Control.LayerSwitcher()],
        projection: new OpenLayers.Projection("EPSG:3857")
    });

    // OSM          


    // GeoJSON

    var geojson = new OpenLayers.Format.GeoJSON({
        'internalProjection': new OpenLayers.Projection("EPSG:3857"),
        'externalProjection': new OpenLayers.Projection("EPSG:4326")
    });



    var geojsonLayer = new OpenLayers.Layer.Vector("GeoJSON", {
        projection: new OpenLayers.Projection("EPSG:4326"),
        isBaseLayer: true
    });
    map.addLayer(geojsonLayer);
var featurecollection...