When a user first signin in Chrome, especially when signing in from first launch prompts, it may take a while for sync to retrieve all the bookmarks. During that time the UI shows no bookmarks which is confusing to the user.

The issue is the transition, from unsigned to signed, where the bookmark model is loaded (aka, you can add bookmarks, open them, rename them) but sync, in the background is quietly updating everything. From a system perspective the current behavior is 100% correct. From a user perspective, not having a progress bar while sync is actively downloading the bookmarks is surprising.

On iOS (And I'm guessing on the other platforms as well) we would like to show to the user that the bookmarks are coming, with a flappy paddle, a message, something instead of a list of empty bookmarks. This is especially jarring when the user signs in from a promo in bookmarks promising all those great features, but ending up empty for a while after sign in.

Right now, to implement this behavior the UI would have to introduce quite a lot of coupling: it would need to observe and track the state of signin, sync and bookmarks. And of course, the details are never simple, the bookmark model may be loaded before or after sign in, etc...

It would be nice to have a unified API, a one method call telling the UI if bookmarks are downloading or will be downloading soon, ideally with a way to show a percentage, and the possibility to register a completion callback.