function replaceTileserver(request) {
  var url = request.url.replace("tile.openstreetmap.org", "tiles.demostat.de");
  console.log("custom-openstreetmap-tile-server: " + request.url + " -> " + url);
  return {redirectUrl: url};
}

urls = [
  "*://*.tile.openstreetmap.org/*"
]


chrome.webRequest.onBeforeRequest.addListener(replaceTileserver, {urls: urls}, ["blocking"]);