(Set)IsOverridingUserAgent should be called on VisibleItem

ios/web/web_state/ui/crw_web_controller.mm

Index: ios/web/web_state/ui/crw_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_web_controller.mm b/ios/web/web_state/ui/crw_web_controller.mm
index bfcc3f987101de631b9de34ac04db4e97a7df7ee..f12d786bc62c841f492660f42620f5e2da70832e 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -458,9 +458,9 @@ @interface CRWWebController ()<CRWContextMenuDelegate,
 
 // Returns YES if the user interacted with the page recently.
 @property(nonatomic, readonly) BOOL userClickedRecently;
-// Returns whether the desktop user agent should be used when setting the user
-// agent.
-@property(nonatomic, readonly) BOOL useDesktopUserAgent;
+
+// Whether or not desktop user agent is used for the visibleItem.
+@property(nonatomic, readonly) BOOL usesDesktopUserAgent;
 
 // Facade for Mojo API.
 @property(nonatomic, readonly) web::MojoFacade* mojoFacade;
@@ -2339,9 +2339,13 @@ - (BOOL)shouldClosePageOnNativeApplicationLoad {
   return rendererInitiatedWithoutInteraction || noNavigationItems;
 }
 
-- (BOOL)useDesktopUserAgent {
-  web::NavigationItem* item = [self currentNavItem];
-  return item && item->IsOverridingUserAgent();
+- (BOOL)usesDesktopUserAgent {
+  if (!self.navigationManagerImpl)
+    return NO;
+
+  web::NavigationItem* visibleItem =
+      self.navigationManagerImpl->GetVisibleItem();
+  return visibleItem && visibleItem->IsOverridingUserAgent();
 }
 
 - (web::MojoFacade*)mojoFacade {
@@ -4214,7 +4218,7 @@ - (WKWebView*)webViewWithConfiguration:(WKWebViewConfiguration*)config {
   // delegate must be specified.
   return web::BuildWKWebView(CGRectZero, config,
                              self.webStateImpl->GetBrowserState(),
-                             [self useDesktopUserAgent]);
+                             self.usesDesktopUserAgent);
 }
 
 - (void)setWebView:(WKWebView*)webView {