Add a function to add extra headers from NavigationThrottle

content/browser/frame_host/navigation_request_info.h

 // Copyright 2014 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 CONTENT_BROWSER_FRAME_HOST_NAVIGATION_REQUEST_INFO_H_
 #define CONTENT_BROWSER_FRAME_HOST_NAVIGATION_REQUEST_INFO_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 14 matching lines @@
   NavigationRequestInfo(const CommonNavigationParams& common_params,
                         const BeginNavigationParams& begin_params,
                         const GURL& first_party_for_cookies,
                         bool is_main_frame,
                         bool parent_is_main_frame,
                         int frame_tree_node_id,
                         scoped_refptr<ResourceRequestBody> request_body);
   ~NavigationRequestInfo();
 
   const CommonNavigationParams common_params;
-  const BeginNavigationParams begin_params;
+
+  // The headers may be changed by NavigationThrottles during calls to
+  // NavigationThrottle::WillStartRequest.
+  BeginNavigationParams begin_params;
 
   // Usually the URL of the document in the top-level window, which may be
   // checked by the third-party cookie blocking policy.
   const GURL first_party_for_cookies;
 
   const bool is_main_frame;
   const bool parent_is_main_frame;
 
   const int frame_tree_node_id;
 
   scoped_refptr<ResourceRequestBody> request_body;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_NAVIGATION_REQUEST_INFO_H_