[iOS][Settings] Fixes Settings background

This CL fixes Settings background when kSettingsRefresh flag is disabled.

Bug: 922511, 1159765
Change-Id: I24c5a26d0a106408ac00df12f33ea0043e060b72
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2596149
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Auto-Submit: Ewann Pellé <ewannpv@chromium.org>
Cr-Commit-Position: refs/heads/master@{#838114}

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

@@ -115,6 +115,10 @@ const CGFloat kActivityIndicatorDimensionIPhone = 56;
 #pragma mark - UIViewController
 
 - (void)viewDidLoad {
+  if (!base::FeatureList::IsEnabled(kSettingsRefresh)) {
+    self.styler.tableViewBackgroundColor =
+        UIColor.cr_systemGroupedBackgroundColor;
+  }
   UIBarButtonItem* flexibleSpace = [[UIBarButtonItem alloc]
       initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace
                            target:nil