function nodeWalkAllPrior(node, predicate, matches) {
  if (!matches) {
    matches = [];
  }
  if (predicate(node)) {
    matches.push(node);
  }
  // Search our earlier siblings and their descendents.
  var parent = node.parentNode;
  if (parent) {
    var idx = parent.childNodes.indexOf(node);
    var siblings = parent.childNodes.slice(0, idx);
    for (var i = siblings.length - 1; i >= 0; i--) {
      _reverseNodeWalkAll(siblings[i], predicate, matches);
    }
    nodeWalkAllPrior(parent, predicate, matches);
  }
  return matches;
}
Equivalent to `nodeWalkAll`, but only returns nodes that are either
ancestors or earlier cousins/siblings in the document.

Nodes are returned in reverse document order, starting from `node`.