text: goog.provide('ol.source.OSM');
  
  goog.require('ol');
  goog.require('ol.Attribution');
  goog.require('ol.source.XYZ');
  
  
  /**
   * @classdesc
   * Layer source for the OpenStreetMap tile server.
   *
   * @constructor
   * @extends {ol.source.XYZ}
   * @param {olx.source.OSMOptions=} opt_options Open Street Map options.
   * @api
   */
  ol.source.OSM = function(opt_options) {
  
    var options = opt_options || {};
  
    var attributions;
    if (options.attributions !== undefined) {
      attributions = options.attributions;
    } else {
      attributions = [ol.source.OSM.ATTRIBUTION];
    }
  
    var crossOrigin = options.crossOrigin !== undefined ?
      options.crossOrigin : 'anonymous';
  
    var url = options.url !== undefined ?
      options.url : 'https://{a-c}.tile.openstreetmap.org/{z}/{x}/{y}.png';
  
    ol.source.XYZ.call(this, {
      attributions: attributions,
      cacheSize: options.cacheSize,
      crossOrigin: crossOrigin,
      opaque: options.opaque !== undefined ? options.opaque : true,
      maxZoom: options.maxZoom !== undefined ? options.maxZoom : 19,
      reprojectionErrorThreshold: options.reprojectionErrorThreshold,
      tileLoadFunction: options.tileLoadFunction,
      url: url,
      wrapX: options.wrapX
    });
  
  };
  ol.inherits(ol.source.OSM, ol.source.XYZ);
  
  
  /**
   * The attribution containing a link to the OpenStreetMap Copyright and License
   * page.
   * @const
   * @type {ol.Attribution}
   * @api
   */
  ol.source.OSM.ATTRIBUTION = new ol.Attribution({
    html: '&copy; ' +
        '<a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> ' +
        'contributors.'
  });
  