[Signin iOS] Handle unnamed account in Account Settings screen.

The account full name might not have been fetched yet. Show the user
email in the meantime.

BUG=656994

Review-Url: https://codereview.chromium.org/2628313003
Cr-Commit-Position: refs/heads/master@{#443560}

ios/chrome/browser/ui/settings/accounts_collection_view_controller.mm

@@ -186,8 +186,7 @@ typedef NS_ENUM(NSInteger, ItemType) {
   if (authenticatedIdentity) {
     title = [authenticatedIdentity userFullName];
     if (!title) {
-      // TODO(crbug.com/656994): Figure how to handle unnamed account.
-      title = @"Unnamed account";
+      title = [authenticatedIdentity userEmail];
     }
   }
   self.title = title;