code: function(chain) {
      var shadows = [], next = this.after(chain[0].from), end = chain[chain.length - 1].to;
      while (true) {
        shadows.push(next);
        var nextNode = next.to;
        if (!nextNode || nextNode == end)
          break;
        else
          next = nextNode.historyAfter || this.before(end);
        // (The this.before(end) is a hack -- FF sometimes removes
        // properties from BR nodes, in which case the best we can hope
        // for is to not break.)
      }
      return shadows;
    }
docs: Find the 'shadow' of a given chain by following the links in the DOM nodes at its start and end.