Replaced NavigationContext::IsErrorPage with NavigationContext::GetError

ios/web/web_state/ui/crw_wk_navigation_states.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/web_state/ui/crw_wk_navigation_states.h"
 
 #include "base/logging.h"
-#include "ios/web/web_state/navigation_context_impl.h"
+#import "ios/web/web_state/navigation_context_impl.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 // Holds a pair of state and creation order index.
 @interface CRWWKNavigationsStateRecord : NSObject {
   // Backs up |context| property.
   std::unique_ptr<web::NavigationContextImpl> _context;
 }
@@ skipping 180 matching lines @@
     }
   }
 
   if (*outNavigation == _nullNavigation) {
     // |_nullNavigation| is a key for storing null navigations.
     *outNavigation = nil;
   }
 }
 
 @end