CL here: https://chromium-review.googlesource.com/c/chromium/src/+/1288542

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cfeea05940f5ddff8d2c411817fdbeb21affe4c3

commit cfeea05940f5ddff8d2c411817fdbeb21affe4c3
Author: Mario Sanchez Prada <mario@igalia.com>
Date: Tue Oct 23 09:38:10 2018

Convert SyncedSessionsObserverBridge to IdentityManager::Observer

Also convert a call to SigninManagerBase::IsAuthenticated() to
IdentityManager::HasPrimaryAccount().

Bug:  887462 
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: Id2d40b7d6e9064a7fa2d64dc3d9a8914d18e795b
Reviewed-on: https://chromium-review.googlesource.com/c/1288542
Commit-Queue: Mario Sanchez Prada <mario@igalia.com>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601890}
[modify] https://crrev.com/cfeea05940f5ddff8d2c411817fdbeb21affe4c3/ios/chrome/browser/sync/BUILD.gn
[modify] https://crrev.com/cfeea05940f5ddff8d2c411817fdbeb21affe4c3/ios/chrome/browser/sync/synced_sessions_bridge.h
[modify] https://crrev.com/cfeea05940f5ddff8d2c411817fdbeb21affe4c3/ios/chrome/browser/sync/synced_sessions_bridge.mm