(Set)IsOverridingUserAgent should be called on VisibleItem

ios/chrome/browser/tabs/tab.mm

Index: ios/chrome/browser/tabs/tab.mm
diff --git a/ios/chrome/browser/tabs/tab.mm b/ios/chrome/browser/tabs/tab.mm
index a6eda18221461e7f4268aae932b9dd11ecab1fdc..5148129643a2544142f5da9c9c146cf425cc2e54 100644
--- a/ios/chrome/browser/tabs/tab.mm
+++ b/ios/chrome/browser/tabs/tab.mm
@@ -1567,13 +1567,16 @@ - (void)openAppStore:(NSString*)appId {
   [storeKitLauncher_ openAppStore:appId];
 }
 
-- (BOOL)useDesktopUserAgent {
-  web::NavigationItem* currentItem = self.currentNavigationItem;
-  return currentItem && currentItem->IsOverridingUserAgent();
+- (BOOL)usesDesktopUserAgent {
+  if (![self navigationManager])

[Eugene But (OOO till 7-30), 2017/02/23 18:00:11]

nit: self.navigationManager because it's a property

[liaoyuke, 2017/02/23 18:37:11]

Done.

+    return NO;
+
+  web::NavigationItem* visibleItem = [self navigationManager]->GetVisibleItem();

[Eugene But (OOO till 7-30), 2017/02/23 18:00:12]

ditto

[liaoyuke, 2017/02/23 18:37:11]

Done.

+  return visibleItem && visibleItem->IsOverridingUserAgent();
 }
 
 - (void)enableDesktopUserAgent {
-  DCHECK_EQ(self.useDesktopUserAgent, NO);
+  DCHECK_EQ(self.usesDesktopUserAgent, NO);
   DCHECK([self navigationManager]);
   [self navigationManager]->OverrideDesktopUserAgentForNextPendingItem();
 }