We've a couple of reports of bookmarks sync never completing. Both of these are in bugs with personal info, so I'm creating this bug so we have an unrestricted bug with the symptoms. The symptoms are, roughly: * As soon as a bookmark operation is performed, sync attempts to do bookmarks, but never completes - the spinner keeps going forever. * Shutting down the browser hangs for a minute before crashing due to a shutdown blocker, with the blocker reporting: > Conditions: [{"name":"PlacesUtils read-only connection closing as part of Places shutdown","state":"1. Service has initiated shutdown" * While in this "syncing forever" state, all bookmark UI in the browser is broken. * Best we can tell from the logging in bug 1469237, we are hanging doing a fetch() of a single bookmark, which really doesn't make any sense. ie, this doesn't appear to be anything to do with reordering (which would be bug 1339390 etc) * Verifying the integrity of the database doesn't help. sql tools appear to believe the database is fine. * At least one user has another desktop profile which does have almost all of the bookmarks synced but which doesn't exhibit the problem. * The issue happens for a user with ~3k bookmarks, which really isn't excessive and is well within the number of bookmarks we expect to work fine with.