code: function listenOnChanges(fn) {
      var scriptContent = 'var cartId="' + me.cart + '";var extId="' + chrome.runtime.id + '";$(document).bind("MenuDishesChanged QuantityChanged MealDealRemoved DishRemoved TipUpdated DiscounCouponAdded AddressSelected DeliveryMethodChanged", ' + fn + ')';
      var script = document.createElement('script');
      script.id = 'tmpScript';
      script.appendChild(document.createTextNode(scriptContent));
      (document.body || document.head || document.documentElement).appendChild(script);
      $("#tmpScript").remove();
  }
docs: ------------ start of web-page context run --------------------
  runs in scope of web-page , sends message to background.js