Implement Reload for ORIGINAL_REQUEST_URL in NavigationManagerImpl.

ios/web/public/reload_type.h

 // Copyright 2017 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.
 
 #ifndef IOS_WEB_PUBLIC_RELOAD_TYPE_H_
 #define IOS_WEB_PUBLIC_RELOAD_TYPE_H_
 
 namespace web {
 
 // Used to specify detailed behavior on requesting reload.
 enum class ReloadType : short {
   // Reloads the visible item.
   NORMAL = 0,
 
-  // Reloads the visible item using the original URL used to create it. This
-  // is used for cases where the user wants to refresh a page using a different
-  // user agent after following a redirect.
+  // Reloads the transient item, or pending item if transient doesn't exist, or
+  // last committed item if both of them don't exist, using the original URL
+  // used to create it. This is used for cases where the user wants to refresh a
+  // page using a different configuration (e.g. user agent).
   ORIGINAL_REQUEST_URL,
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_RELOAD_TYPE_H_