Currently, RangeBoundaryBase can store either only mRef or mOffset. However, == operator of RangeBoudaryBase still compares mRef simply. However, if one has only mRef and the other has only mOffset, it returns false. This patch makes == operator checks if both mOffset have been set. If so, this checks both mOffset.value() and mRef are matched. However, if mRef of only one of them is nullptr, this doesn't make it check mRef because computing mRef needs some cost and initializing mRef from the other fixes the referring child stronger. If the user of the operator sets only mOffset and wait DOM tree changes, computing mRef may break such callers. If one has only mRef and the other has only mOffset, this patch makes it compute mRef. This is not the best behavior, perhaps. However, there is no way to compare these instances. If this becomes a problem, we should make it create temporary instance, but it'll waste runtime cost. So, let's avoid using this approach for now. Finally, making it check both mRef simply. Review commit: https://reviewboard.mozilla.org/r/197560/diff/#index_header See other reviews: https://reviewboard.mozilla.org/r/197560/