UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.113 Whale/1.0.39.16 Safari/537.36

Steps to reproduce the problem:
With relatively large bookmarks, say over 10000, bookmark deletion could take much time if LoopbackServer is used for sync.

What is the expected behavior?

What went wrong?
When a bookmark node is removed, its children seems guaranteed to be removed. 
(See BookmarkChangeProcessor::OnWillRemoveBookmarks. It calls RemoveSyncNodeHierarchy and it calls RemoveAllChildNodes)
So, if a bookmark folder that contains 99 bookmarks is removed, LoopbackServer::CommitEntity() and DeleteChildren() are called 100 times unnecessarily and this results in 100x100 invoking of LoopbackServer::IsChild() because DeleteChildren() traverses all entities, which could be a performance problem with heavy bookmark users.

Did this work before? N/A 

Chrome version: 60.0.3112.113  Channel: stable
OS Version: OS X 10.13.2
Flash Version: Shockwave Flash 28.0 r0