CL here: https://chromium-review.googlesource.com/c/chromium/src/+/1332300

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/dfa24463770d4c005dbc1551f0826591b13b1b69

commit dfa24463770d4c005dbc1551f0826591b13b1b69
Author: Mario Sanchez Prada <mario@igalia.com>
Date: Tue Nov 13 17:53:59 2018

Migrate SyncedBookmarksObserverBridge to the IdentityManager

Replace usage of SigninManagerBase::IsAuthenticated with
IdentityManager::HasPrimaryAccount().

Bug:  903840 
Change-Id: I907301ebe26df1a1b7c718a30ec0051b26a5ad55
Reviewed-on: https://chromium-review.googlesource.com/c/1332300
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Mario Sanchez Prada <mario@igalia.com>
Cr-Commit-Position: refs/heads/master@{#607645}
[modify] https://crrev.com/dfa24463770d4c005dbc1551f0826591b13b1b69/ios/chrome/browser/ui/bookmarks/synced_bookmarks_bridge.h
[modify] https://crrev.com/dfa24463770d4c005dbc1551f0826591b13b1b69/ios/chrome/browser/ui/bookmarks/synced_bookmarks_bridge.mm