old_contents: chrome.extension.onRequest.addListener(function(request, sender, sendResponse) {
    if (request.method == "getStringerURLs") {
      sendResponse({urls: [
        "stringer.bitboxer.de"
      ]});
    } else {
      sendResponse({});
    }
  });
  
new_contents: chrome.extension.onRequest.addListener(function(request, sender, sendResponse) {
    if (request.method == "getStringerURLs") {
      sendResponse({urls: [
        JSON.parse(localStorage["urls"])
      ]});
    } else {
      sendResponse({});
    }
  });
  
subject: load data from localstorage