track clicks on tiles

tiles_track.js

    this._linksReporterMod = new PageMod({
      attachTo: ["existing", "top"],
      contentScript: `links = document.querySelectorAll('.newtab-site')
                      function log_events(pos) {
                        return function log(e) {
                          var target = e.target;
                          var type;
                          while (target) {
                            if (target.tagName === 'a' || target.href) {
                              type = target.parentNode.getAttribute('type');
                              self.port.emit("tile-click", {
                                action: "CLICK",
                                position: pos,
                                source: type
                              });
                              break;
                            }
                            target = target.parentNode;
                          }
                          e.preventDefault();
                          return false;
                        }
                      }
                      
                      for (var i = 0; i < links.length; i++) {
                        links[i].addEventListener("click", log_events(i));
                      }`,
      include: "about:newtab",
      onAttach(worker) {
        worker.port.on("tile-click", e => reportSitesAction(e));
      }
    });