Carregamento preguiçoso usando web worker - https://github.com/mattslocum/ng-webworker

lazy.js

(function () {
  'use strict';
  angular.module('clusbe.diretiva.lazy', [])
    .directive('lazy', [
      '$http',
      '$timeout',
      'Webworker',
      'CONSTANT_RESOURCES_URL_IMG',
      'CONSTANT_BASE_URL',
      '$window',
      function ($http,
                $timeout,
                Webworker,
                CONSTANT_RESOURCES_URL_IMG,
                CONSTANT_BASE_URL,
                $window) {

        // Função que faz a resolução de um recurso
        // params uri
        function workerMock(url, data) {
          var xmlhttp = new XMLHttpRequest();
          xmlhttp.onreadystatechange = function () {
            if (this.readyState == 4 && this.status == 200) {
              complete(this.response);
            } else {
              notify(this.status);
            }
          };


          if (data) {
            xmlhttp.open("POST", url, true);
            xmlhttp.setRequestHeader("Content-type", "application/json");
            xmlhttp.send(JSON.stringify(data));
          } else {
            xmlhttp.open("GET", url, true);
            xmlhttp.send();
          }
        }

        // Função que executa o worker de resolução de uma url
        // Tarefa executado em paralelo - Multithread
        function _exec(worker, url, callback) {
          worker.run(url).then(function (response) {
            callback(null, response);
          }, function (err) {
            callback(err, null);
          });
        }

        // Função de link para a renderização da view
        var _link = function (scope, element, atrrs) {

          var tagName = element.prop('tagName');

          tagName === 'IMG' ? element.prop('src', 'img/loading_spinner.svg') : element.css({'background-image': 'url(img/loading_spinner.svg)'});
          var WorkerHttpThead = Webworker.create(workerMock, {async: true});

          var _callback = function (err, response) {
            if (err) element.prop('src', 'img/reload.svg');
            try {
              response = JSON.parse(response);
            } catch (e) {
            }

            var tempUrl = response && response.url;

            try {
              if (tempUrl) {
                if (tempUrl.indexOf('images/cache') !== -1) tempUrl = CONSTANT_RESOURCES_URL_IMG + response.url.replace('images/cache', 'images');
                else if (tempUrl.indexOf('images/data') !== -1) tempUrl = CONSTANT_RESOURCES_URL_IMG + response.url.replace('images/data', 'image');
                else tempUrl = CONSTANT_RESOURCES_URL_IMG + tempUrl;
              } else {
                tempUrl = (atrrs.lazy.match(/perfil/) ? 'img/avatar.svg' : 'img/reload.svg');
              }
            } catch (e) {
            }

            var image = new Image();
            image.src = tempUrl;

            image.onload = function (event) {
              tagName === 'IMG' ? element.prop('src', tempUrl) : element.css({'background-image': 'url(' + tempUrl + ')'});
            };

            image.onerror = function (event) {
              var img = (atrrs.lazy.match(/perfil/) ? 'img/avatar.svg' : 'img/reload.svg');
              tagName === 'IMG' ? element.prop('src', img) : element.css({'background-image': 'url(' + img + ')'});
            }
          };

          // Fica observando alterações que ocorrem na view
          atrrs.$observe('lazy', function () {
            var regex_a = atrrs.lazy ? atrrs.lazy.match(/\B[\//\//]/) : undefined;
            var regex_b = atrrs.lazy ? atrrs.lazy.match(/\b[\//]+$/) : undefined;
            if (!regex_a && !regex_b) {
              if (atrrs.lazy.indexOf('videos/data') !== -1) _callback(null, {url: (atrrs.lazy.replace('videos/data', 'videos')).replace('mp4', 'png')});
              else _exec(WorkerHttpThead, CONSTANT_BASE_URL + atrrs.lazy + (atrrs.lazy.match(/post/) ? ("/" + $window.innerWidth) : ''), _callback);
            }
          });
        };

        return {
          strict: 'A',
          link: _link
        }
      }]);
})();

// ------------ Este é o erro que estou obtendo: ---------------
/*
 Uncaught ReferenceError: notify is not defined
    at XMLHttpRequest.xmlhttp.onreadystatechange (3a936af9-bb74-4043-ab69-0c01ddb94c37:7)
    at workerMock (3a936af9-bb74-4043-ab69-0c01ddb94c37:17)
    at onmessage (3a936af9-bb74-4043-ab69-0c01ddb94c37:20)
*/