Bug 239499

Currently, we do try to prevent performing duplicate updates, but we do so only if we have an exact match for a previous notification for any given object:

case AXTextChanged:
case AXValueChanged: {

    bool needsUpdate = appendIfNotContainsMatching(filteredNotifications, notification, [&notification] (const std::pair<RefPtr<AXCoreObject>, AXNotification>& note) {
       return note.second == notification.second && note.first.get() == notification.first.get();
    });

    if (needsUpdate)
        tree->updateNode(*notification.first);
   

However, multiple notifications trigger AXIsolatedTree::updateNode and children, so we'll still do wasted work in this case. For example, in the above snippet, we'd update the node twice if the same object got both an AXTextChanged and AXValueChanged notification in the same batch.