code: function getMceInternalContent(e) {
          var internalContent;
  
          if (e.dataTransfer) {
            internalContent = e.dataTransfer.getData(mceInternalDataType);
  
            if (internalContent && internalContent.indexOf(mceInternalUrlPrefix) >= 0) {
              internalContent = internalContent.substr(mceInternalUrlPrefix.length).split(',');
  
              return {
                id: unescape(internalContent[0]),
                html: unescape(internalContent[1])
              };
            }
          }
  
          return null;
        }
docs: Gets content of special data:text/mce-internal url on the event's dataTransfer object.
  This is to workaround the inability to set custom contentType on IE and Safari.
  The editor's selected content is encoded into this url so drag and drop between editors will work.
  
  @private
  @param {DragEvent} e Event object
  @returns {String} mce-internal content