// Find the previous layout object that has the multicol container in its containing block chain, skipping nested multicol containers.
static LayoutObject* previousInPreOrderSkippingOutOfFlow(LayoutMultiColumnFlowThread* flowThread, LayoutObject* descendant)
{
    ASSERT(descendant->isDescendantOf(flowThread));
    LayoutObject* object = descendant->previousInPreOrder(flowThread);
    while (object && object != flowThread) {
        if (object->isColumnSpanAll()) {
            LayoutMultiColumnFlowThread* placeholderFlowThread = toLayoutBox(object)->spannerPlaceholder()->flowThread();
            if (placeholderFlowThread == flowThread)
                break;
            // We're inside an inner multicol container. We have no business there. Continue on the outside.
            object = placeholderFlowThread->parent();
            ASSERT(object->isDescendantOf(flowThread));
            continue;
        }
        if (object->flowThreadContainingBlock() == flowThread) {
            LayoutObject* ancestor;
            for (ancestor = object->parent(); ; ancestor = ancestor->parent()) {
                if (ancestor == flowThread)
                    return object;
                if (isMultiColumnContainer(*ancestor)) {
                    // We're inside an inner multicol container. We have no business there.
                    break;
                }
            }
            object = ancestor;
            ASSERT(ancestor->isDescendantOf(flowThread));
            continue; // Continue on the outside of the inner flow thread.
        }
        // We're inside something that's out-of-flow. Keep looking upwards and backwards in the tree.
        object = object->previousInPreOrder(flowThread);
    }
    if (!object || object == flowThread)
        return nullptr;
#if ENABLE(ASSERT)
    // Make sure that we didn't stumble into an inner multicol container.
    for (LayoutObject* walker = object->parent(); walker && walker != flowThread; walker = walker->parent())
        ASSERT(!isMultiColumnContainer(*walker));
#endif
    return object;
}