Revert of Remove reference counting from HttpNetworkSession.

net/http/http_network_layer.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 NET_HTTP_HTTP_NETWORK_LAYER_H_
 #define NET_HTTP_HTTP_NETWORK_LAYER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/power_monitor/power_observer.h"
 #include "base/threading/non_thread_safe.h"
 #include "net/base/net_export.h"
 #include "net/http/http_transaction_factory.h"
 
 namespace net {
 
 class HttpNetworkSession;
 
 class NET_EXPORT HttpNetworkLayer
     : public HttpTransactionFactory,
       public base::PowerObserver,
       NON_EXPORTED_BASE(public base::NonThreadSafe) {
  public:
   // Construct a HttpNetworkLayer with an existing HttpNetworkSession which
-  // contains a valid ProxyService. The HttpNetworkLayer must be destroyed
-  // before |session|.
+  // contains a valid ProxyService.
   explicit HttpNetworkLayer(HttpNetworkSession* session);
   ~HttpNetworkLayer() override;
 
+  // Create a transaction factory that instantiate a network layer over an
+  // existing network session. Network session contains some valuable
+  // information (e.g. authentication data) that we want to share across
+  // multiple network layers. This method exposes the implementation details
+  // of a network layer, use this method with an existing network layer only
+  // when network session is shared.
+  static HttpTransactionFactory* CreateFactory(HttpNetworkSession* session);
+
   // HttpTransactionFactory methods:
   int CreateTransaction(RequestPriority priority,
                         scoped_ptr<HttpTransaction>* trans) override;
   HttpCache* GetCache() override;
   HttpNetworkSession* GetSession() override;
 
   // base::PowerObserver methods:
   void OnSuspend() override;
   void OnResume() override;
 
  private:
-  HttpNetworkSession* const session_;
+  const scoped_refptr<HttpNetworkSession> session_;
   bool suspended_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpNetworkLayer);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_NETWORK_LAYER_H_