Provide mutable members of UrlRequestContext via pure-virtual interface

sync/internal_api/public/http_bridge.h

 // Copyright (c) 2012 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 SYNC_INTERNAL_API_PUBLIC_HTTP_BRIDGE_H_
 #define SYNC_INTERNAL_API_PUBLIC_HTTP_BRIDGE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 40 matching lines @@
     // currently active profile.
     RequestContext(
         net::URLRequestContext* baseline_context,
         const scoped_refptr<base::SingleThreadTaskRunner>&
             network_task_runner,
         const std::string& user_agent);
 
     // The destructor MUST be called on the IO thread.
     virtual ~RequestContext();
 
-    virtual const std::string& GetUserAgent(const GURL& url) const OVERRIDE;
-
    private:
     net::URLRequestContext* const baseline_context_;
     const scoped_refptr<base::SingleThreadTaskRunner> network_task_runner_;
-    const std::string user_agent_;
+    scoped_ptr<net::ConstHttpUserAgentSettings>
+        const_http_user_agent_settings_;
 
     DISALLOW_COPY_AND_ASSIGN(RequestContext);
   };
 
   // Lazy-getter for RequestContext objects.
   class RequestContextGetter : public net::URLRequestContextGetter {
    public:
     RequestContextGetter(
         net::URLRequestContextGetter* baseline_context_getter,
         const std::string& user_agent);
@@ skipping 145 matching lines @@
 
   const scoped_refptr<HttpBridge::RequestContextGetter>
       request_context_getter_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpBridgeFactory);
 };
 
 }  //  namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_HTTP_BRIDGE_H_