Allow URLRequests from one context to have different NetworkDelegates.

net/url_request/url_request_context.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.
 
 // This class represents contextual information (cookies, cache, etc.)
 // that's useful when processing resource requests.
 // The class is reference-counted so that it can be cleaned up after any
 // requests that are using it have been completed.
 
 #ifndef NET_URL_REQUEST_URL_REQUEST_CONTEXT_H_
@@ skipping 41 matching lines @@
  public:
   URLRequestContext();
   virtual ~URLRequestContext();
 
   // Copies the state from |other| into this context.
   void CopyFrom(const URLRequestContext* other);
 
   // May return NULL if this context doesn't have an associated network session.
   const HttpNetworkSession::Params* GetNetworkSessionParams() const;
 
-  // Creates a URLRequest. |cookie_store| optionally specifies a cookie store
-  // to be used rather than the one represented by the context, or NULL
-  // otherwise.
+  // Creates a URLRequest. If |cookie_store| is non-NULL, it will be used
+  // instead of the context's cookie store.
   scoped_ptr<URLRequest> CreateRequest(const GURL& url,
                                        RequestPriority priority,
                                        URLRequest::Delegate* delegate,
                                        CookieStore* cookie_store) const;
 
   NetLog* net_log() const {
     return net_log_;
   }
 
   void set_net_log(NetLog* net_log) {
@@ skipping 172 matching lines @@
   // ---------------------------------------------------------------------------
 
   scoped_ptr<std::set<const URLRequest*> > url_requests_;
 
   DISALLOW_COPY_AND_ASSIGN(URLRequestContext);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_CONTEXT_H_