function deleteNext() {
    Blockly.Events.setGroup(eventGroup);
    var block = deleteList.shift();
    if (block) {
      if (block.workspace) {
        block.dispose(false, true);
        setTimeout(deleteNext, DELAY);
      } else {
        deleteNext();
      }
    }
    Blockly.Events.setGroup(false);
  }
Show the context menu for the workspace.
@param {!Event} e Mouse event.
@private