Cesiumjs memory leak

ArcGIS layer issue

HTML

<script src="http://cesiumjs.org/Cesium/Build/CesiumUnminified/Cesium.js"></script>
<div id=cesiumContainer></div>

CSS

html, body {
    margin: 0;
    padding: 0;
    height: 100%;
}

#cesiumContainer, .cesium-viewer,
.cesium-viewer-cesiumWidgetContainer, .cesium-widget,
.cesium-widget canvas {
    width: 100%;
    height: 100%;
}

JavaScript

var viewer = new Cesium.Viewer('cesiumContainer', {
        baseLayerPicker: false,
        fullscreenButton: false,
        homeButton: false,
        sceneModePicker: false,
        selectionIndicator: false,
        timeline: false,
        animation: false,
        geocoder: false
});


	var layers = viewer.scene.imageryLayers;
layers.addImageryProvider(new Cesium.ArcGisMapServerImageryProvider({
							url : 'https://maps.ngdc.noaa.gov/arcgis/rest/services/web_mercator/gebco_2014_contours/MapServer'
						}));