text: /**
   * Given a DOM subtree, wraps it in a list, and puts each line into its own
   * list item.
   *
   * @param {Node} node modified in place.  Its content is pulled into an
   *     HTMLOListElement, and each line is moved into a separate list item.
   *     This requires cloning elements, so the input might not have unique
   *     IDs after numbering.
   * @param {number|null|boolean} startLineNum
   *     If truthy, coerced to an integer which is the 1-indexed line number
   *     of the first line of code.  The number of the first line will be
   *     attached to the list.
   * @param {boolean} isPreformatted true iff white-space in text nodes should
   *     be treated as significant.
   */
  function numberLines(node, startLineNum, isPreformatted) {
    var nocode = /(?:^|\s)nocode(?:\s|$)/;
    var lineBreak = /\r\n?|\n/;
  
    var document = node.ownerDocument;
  
    var li = document.createElement('li');
    while (node.firstChild) {
      li.appendChild(node.firstChild);
    }
    // An array of lines.  We split below, so this is initialized to one
    // un-split line.
    var listItems = [li];
  
    function walk(node) {
      var type = node.nodeType;
      if (type == 1 && !nocode.test(node.className)) {  // Element
        if ('br' === node.nodeName.toLowerCase()) {
          breakAfter(node);
          // Discard the <BR> since it is now flush against a </LI>.
          if (node.parentNode) {
            node.parentNode.removeChild(node);
          }
        } else {
          for (var child = node.firstChild; child; child = child.nextSibling) {
            walk(child);
          }
        }
      } else if ((type == 3 || type == 4) && isPreformatted) {  // Text
        var text = node.nodeValue;
        var match = text.match(lineBreak);
        if (match) {
          var firstLine = text.substring(0, match.index);
          node.nodeValue = firstLine;
          var tail = text.substring(match.index + match[0].length);
          if (tail) {
            var parent = node.parentNode;
            parent.insertBefore(
              document.createTextNode(tail), node.nextSibling);
          }
          breakAfter(node);
          if (!firstLine) {
            // Don't leave blank text nodes in the DOM.
            node.parentNode.removeChild(node);
          }
        }
      }
    }
  
    // Split a line after the given node.
    function breakAfter(lineEndNode) {
      // If there's nothing to the right, then we can skip ending the line
      // here, and move root-wards since splitting just before an end-tag
      // would require us to create a bunch of empty copies.
      while (!lineEndNode.nextSibling) {
        lineEndNode = lineEndNode.parentNode;
        if (!lineEndNode) { return; }
      }
  
      function breakLeftOf(limit, copy) {
        // Clone shallowly if this node needs to be on both sides of the break.
        var rightSide = copy ? limit.cloneNode(false) : limit;
        var parent = limit.parentNode;
        if (parent) {
          // We clone the parent chain.
          // This helps us resurrect important styling elements that cross lines.
          // E.g. in <i>Foo<br>Bar</i>
          // should be rewritten to <li><i>Foo</i></li><li><i>Bar</i></li>.
          var parentClone = breakLeftOf(parent, 1);
          // Move the clone and everything to the right of the original
          // onto the cloned parent.
          var next = limit.nextSibling;
          parentClone.appendChild(rightSide);
          for (var sibling = next; sibling; sibling = next) {
            next = sibling.nextSibling;
            parentClone.appendChild(sibling);
          }
        }
        return rightSide;
      }
  
      var copiedListItem = breakLeftOf(lineEndNode.nextSibling, 0);
  
      // Walk the parent chain until we reach an unattached LI.
      for (var parent;
           // Check nodeType since IE invents document fragments.
           (parent = copiedListItem.parentNode) && parent.nodeType === 1;) {
        copiedListItem = parent;
      }
      // Put it on the list of lines for later processing.
      listItems.push(copiedListItem);
    }
  
    // Split lines while there are lines left to split.
    for (var i = 0;  // Number of lines that have been split so far.
         i < listItems.length;  // length updated by breakAfter calls.
         ++i) {
      walk(listItems[i]);
    }
  
    // Make sure numeric indices show correctly.
    if (startLineNum === (startLineNum|0)) {
      listItems[0].setAttribute('value', startLineNum);
    }
  
    var ol = document.createElement('ol');
    ol.className = 'linenums';
    var offset = Math.max(0, ((startLineNum - 1 /* zero index */)) | 0) || 0;
    for (var i = 0, n = listItems.length; i < n; ++i) {
      li = listItems[i];
      // Stick a class on the LIs so that stylesheets can
      // color odd/even rows, or any other row pattern that
      // is co-prime with 10.
      li.className = 'L' + ((i + offset) % 10);
      if (!li.firstChild) {
        li.appendChild(document.createTextNode('\xA0'));
      }
      ol.appendChild(li);
    }
  
    node.appendChild(ol);
  }
  