code: function _moveView(sourcePaneId, destinationPaneId, file, destinationIndex) {
          var result = new $.Deferred(),
              sourcePane = _getPane(sourcePaneId),
              destinationPane = _getPane(destinationPaneId);
  
          sourcePane.moveView(file, destinationPane, destinationIndex)
              .done(function () {
                  // remove existing entry from mrulist for the same document if present 
                  _removeFileFromMRU(destinationPane.id, file);
                  // update the mru list
                  _mruList.every(function (record) {
                      if (record.file === file && record.paneId === sourcePane.id) {
                          record.paneId = destinationPane.id;
                          return false;
                      }
                      return true;
                  });
                  exports.trigger("workingSetMove", file, sourcePane.id, destinationPane.id);
                  result.resolve();
              });
  
          return result.promise();
      }
docs: moves a view from one pane to another
  @param {!string} sourcePaneId - id of the source pane
  @param {!string} destinationPaneId - id of the destination pane
  @param {!File} file - the File to move
  @param {Number} destinationIndex - the working set index of the file in the destination pane
  @return {jQuery.Promise} a promise that resolves when the move has completed.
  @private