code: function getSource (url) {
              if (!_has(sourceCache, url)) {
                  // URL needs to be able to fetched within the acceptable domain.  Otherwise,
                  // cross-domain errors will be triggered.
                  var source = '';
  
                  url = url || "";
  
                  if (url.indexOf && url.indexOf(document.domain) !== -1) {
                      source = loadSource(url);
                  }
                  sourceCache[url] = source ? source.split('\n') : [];
              }
  
              return sourceCache[url];
          }
docs: Retrieves source code from the source code cache.
  @param {string} url URL of source code.
  @return {Array.<string>} Source contents.