[iOS] Disclosure indicator missing in sign-in item

The sign-in cell opens to the account list view controller, it needs to
have a disclosure indicator.
Before:
https://drive.google.com/open?id=1Opqj8IeHkqfeIbrb5ayizQxk3YFL4p6g
After:
https://drive.google.com/open?id=1VOoQgkNrnNaexALS-Dprvn6H4YjyDQrH

Bug: 914059
Change-Id: I50616173dd5fb6eb457005518e096cc084bcd721
TBR: gambard
Reviewed-on: https://chromium-review.googlesource.com/c/1489204Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635676}

ios/chrome/browser/ui/settings/google_services/google_services_settings_mediator.mm

@@ -191,6 +191,7 @@ NSString* kGoogleServicesSyncErrorImage = @"google_services_sync_error";
   DCHECK(!self.accountItem);
   self.accountItem =
       [[TableViewAccountItem alloc] initWithType:IdentityItemType];
+  self.accountItem.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
   [model addItem:self.accountItem
       toSectionWithIdentifier:IdentitySectionIdentifier];
 }