Set user agent type of transient item the same as pending item.

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 b5e12d3765c2add415dff86d912e2a3beaf136a6..c709909a13791a84955f36205153827c4ba6b21f 100644
--- a/ios/chrome/browser/tabs/tab.mm
+++ b/ios/chrome/browser/tabs/tab.mm
@@ -1479,9 +1479,15 @@ - (BOOL)usesDesktopUserAgent {
   if (!self.navigationManager)
     return NO;
 
-  web::NavigationItem* visibleItem = self.navigationManager->GetVisibleItem();
-  return visibleItem &&
-         visibleItem->GetUserAgentType() == web::UserAgentType::DESKTOP;
+  web::NavigationItem* item = nullptr;

[Eugene But (OOO till 7-30), 2017/03/30 23:01:49]

How about this?:

web::NavigationItem* item = self.navigationManager->GetTransientItem();
if (!item)
  item = self.navigationManager->GetPendingItem();
if (!item)
  item = self.navigationManager->GetLastCommittedItem();

[liaoyuke, 2017/03/31 15:50:12]

Done.

+  if (self.navigationManager->GetTransientItem())
+    item = self.navigationManager->GetTransientItem();
+  else if (self.navigationManager->GetPendingItem())
+    item = self.navigationManager->GetPendingItem();
+  else if (self.navigationManager->GetLastCommittedItem())
+    item = self.navigationManager->GetLastCommittedItem();
+
+  return item && item->GetUserAgentType() == web::UserAgentType::DESKTOP;
 }
 
 - (void)enableDesktopUserAgent {