Add histogram to measure the read deferral on crosswebsite navigation

content/browser/loader/resource_loader.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 CONTENT_BROWSER_LOADER_RESOURCE_LOADER_H_
 #define CONTENT_BROWSER_LOADER_RESOURCE_LOADER_H_
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 109 matching lines @@
   scoped_ptr<net::URLRequest> request_;
   scoped_ptr<ResourceHandler> handler_;
   ResourceLoaderDelegate* delegate_;
 
   scoped_refptr<ResourceDispatcherHostLoginDelegate> login_delegate_;
   scoped_refptr<SSLClientAuthHandler> ssl_client_auth_handler_;
 
   uint64 last_upload_position_;
   bool waiting_for_upload_progress_ack_;
   base::TimeTicks last_upload_ticks_;
+  base::TimeTicks read_deferral_start_time_;
 
   // Indicates that we are in a state of being transferred to a new downstream
   // consumer.  We are waiting for a notification to complete the transfer, at
   // which point we'll receive a new ResourceHandler.
   bool is_transferring_;
 
   scoped_ptr<net::ClientCertStore> client_cert_store_;
 
   base::WeakPtrFactory<ResourceLoader> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ResourceLoader);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_LOADER_RESOURCE_LOADER_H_