Add a NavigationThrottle to the public content/ interface

content/browser/frame_host/navigation_request.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_H_
 #define CONTENT_BROWSER_FRAME_HOST_NAVIGATION_REQUEST_H_
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 146 matching lines @@
   void OnRequestFailed(bool has_stale_copy_in_cache, int net_error) override;
   void OnRequestStarted(base::TimeTicks timestamp) override;
 
   FrameTreeNode* frame_tree_node_;
 
   // Initialized on creation of the NavigationRequest. Sent to the renderer when
   // the navigation is ready to commit.
   // Note: When the navigation is ready to commit, the url in |common_params|
   // will be set to the final navigation url, obtained after following all
   // redirects.
+  // Note: |common_params_| and |begin_params_| are not const as they can be
+  // modified during redirects.
   CommonNavigationParams common_params_;
-  const BeginNavigationParams begin_params_;
+  BeginNavigationParams begin_params_;
   const RequestNavigationParams request_params_;
   const bool browser_initiated_;
 
   NavigationState state_;
 
 
   // The parameters to send to the IO thread. |loader_| takes ownership of
   // |info_| after calling BeginNavigation.
   scoped_ptr<NavigationRequestInfo> info_;
 
   scoped_ptr<NavigationURLLoader> loader_;
 
   // These next items are used in browser-initiated navigations to store
   // information from the NavigationEntryImpl that is required after request
   // creation time.
   scoped_refptr<SiteInstanceImpl> source_site_instance_;
   scoped_refptr<SiteInstanceImpl> dest_site_instance_;
   NavigationEntryImpl::RestoreType restore_type_;
   bool is_view_source_;
   int bindings_;
 
   scoped_ptr<NavigationHandleImpl> navigation_handle_;
 
   DISALLOW_COPY_AND_ASSIGN(NavigationRequest);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_NAVIGATION_REQUEST_H_