code: function _markTags(cm, node) {
          node.children.forEach(function (childNode) {
              if (childNode.isElement()) {
                  _markTags(cm, childNode);
              }
          });
          var mark = cm.markText(node.startPos, node.endPos);
          mark.tagID = node.tagID;
      }
docs: Recursively walks the SimpleDOM starting at node and marking
  all tags in the CodeMirror instance. The more useful interface
  is the _markTextFromDOM function which clears existing marks
  before calling this function to create new ones.
  
  @param {CodeMirror} cm CodeMirror instance in which to mark tags
  @param {Object} node SimpleDOM node to use as the root for marking