Display the preload Tab if it replaces the current Tab.

ios/chrome/browser/ui/browser_view_controller.mm

Index: ios/chrome/browser/ui/browser_view_controller.mm
diff --git a/ios/chrome/browser/ui/browser_view_controller.mm b/ios/chrome/browser/ui/browser_view_controller.mm
index 83513d14823aefbee845c27c18342b1700d6507d..e83a5c533d0229abb781bda7b73f1fea507fd3f9 100644
--- a/ios/chrome/browser/ui/browser_view_controller.mm
+++ b/ios/chrome/browser/ui/browser_view_controller.mm
@@ -4574,6 +4574,10 @@ - (void)tabModel:(TabModel*)model
           atIndex:(NSUInteger)index {
   [self uninstallDelegatesForTab:oldTab];
   [self installDelegatesForTab:newTab];
+
+  // Add |newTab|'s view to the hierarchy if it's the current Tab.
+  if (self.active && model.currentTab == newTab)
+    [self displayTab:newTab isNewSelection:NO];
 }
 
 // A tab has been removed, remove its views from display if necessary.