function recombineTagsAndDecorations(job) {
    var isIE8OrEarlier = /\bMSIE\s(\d+)/.exec(navigator.userAgent);
    isIE8OrEarlier = isIE8OrEarlier && +isIE8OrEarlier[1] <= 8;
    var newlineRe = /\n/g;
  
    var source = job.sourceCode;
    var sourceLength = source.length;
    // Index into source after the last code-unit recombined.
    var sourceIndex = 0;
  
    var spans = job.spans;
    var nSpans = spans.length;
    // Index into spans after the last span which ends at or before sourceIndex.
    var spanIndex = 0;
  
    var decorations = job.decorations;
    var nDecorations = decorations.length;
    // Index into decorations after the last decoration which ends at or before
    // sourceIndex.
    var decorationIndex = 0;
  
    // Remove all zero-length decorations.
    decorations[nDecorations] = sourceLength;
    var decPos, i;
    for (i = decPos = 0; i < nDecorations;) {
      if (decorations[i] !== decorations[i + 2]) {
        decorations[decPos++] = decorations[i++];
        decorations[decPos++] = decorations[i++];
      } else {
        i += 2;
      }
    }
    nDecorations = decPos;
  
    // Simplify decorations.
    for (i = decPos = 0; i < nDecorations;) {
      var startPos = decorations[i];
      // Conflate all adjacent decorations that use the same style.
      var startDec = decorations[i + 1];
      let end = i + 2;
      while (end + 2 <= nDecorations && decorations[end + 1] === startDec) {
        end += 2;
      }
      decorations[decPos++] = startPos;
      decorations[decPos++] = startDec;
      i = end;
    }
  
    decorations.length = decPos;
  
    var sourceNode = job.sourceNode;
    var oldDisplay;
    if (sourceNode) {
      oldDisplay = sourceNode.style.display;
      sourceNode.style.display = 'none';
    }
    try {
      decoration = null;
      while (spanIndex < nSpans) {
        var spanEnd = spans[spanIndex + 2] || sourceLength;
  
        var decEnd = decorations[decorationIndex + 2] || sourceLength;
  
        const end = Math.min(spanEnd, decEnd);
  
        var textNode = spans[spanIndex + 1];
        var styledText;
        if (textNode.nodeType !== 1  // Don't muck with <BR>s or <LI>s
            // Don't introduce spans around empty text nodes.
            && (styledText = source.substring(sourceIndex, end))) {
          // This may seem bizarre, and it is.  Emitting LF on IE causes the
          // code to display with spaces instead of line breaks.
          // Emitting Windows standard issue linebreaks (CRLF) causes a blank
          // space to appear at the beginning of every line but the first.
          // Emitting an old Mac OS 9 line separator makes everything spiffy.
          if (isIE8OrEarlier) {
            styledText = styledText.replace(newlineRe, '\r');
          }
          textNode.nodeValue = styledText;
          var document = textNode.ownerDocument;
          var span = document.createElement('span');
          span.className = decorations[decorationIndex + 1];
          var parentNode = textNode.parentNode;
          parentNode.replaceChild(span, textNode);
          span.appendChild(textNode);
          if (sourceIndex < spanEnd) {  // Split off a text node.
            spans[spanIndex + 1] = textNode
                // TODO: Possibly optimize by using '' if there's no flicker.
                = document.createTextNode(source.substring(end, spanEnd));
            parentNode.insertBefore(textNode, span.nextSibling);
          }
        }
  
        sourceIndex = end;
  
        if (sourceIndex >= spanEnd) {
          spanIndex += 2;
        }
        if (sourceIndex >= decEnd) {
          decorationIndex += 2;
        }
      }
    } finally {
      if (sourceNode) {
        sourceNode.style.display = oldDisplay;
      }
    }
  }
Breaks {@code job.sourceCode} around style boundaries in
{@code job.decorations} and modifies {@code job.sourceNode} in place.
@param {Object} job like <pre>{
   sourceCode: {string} source as plain text,
   sourceNode: {HTMLElement} the element containing the source,
   spans: {Array.<number|Node>} alternating span start indices into source
      and the text node or element (e.g. {@code <BR>}) corresponding to that
      span.
   decorations: {Array.<number|string} an array of style classes preceded
      by the position at which they start in job.sourceCode in order
}</pre>
@private