Add a histogram to record the dns resolution + tcp connection times.

net/http/http_network_transaction.h

 // Copyright (c) 2006-2008 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_TRANSACTION_H_
 #define NET_HTTP_HTTP_NETWORK_TRANSACTION_H_
 
 #include <string>
 
 #include "base/ref_counted.h"
@@ skipping 70 matching lines @@
   int DoWriteHeadersComplete(int result);
   int DoWriteBody();
   int DoWriteBodyComplete(int result);
   int DoReadHeaders();
   int DoReadHeadersComplete(int result);
   int DoReadBody();
   int DoReadBodyComplete(int result);
   int DoDrainBodyForAuthRestart();
   int DoDrainBodyForAuthRestartComplete(int result);
 
-  // Record histogram of time to acquire a TCP connection.
-  void LogTCPConnectionMetrics() const;
+  // Record histograms of latency until Connect() completes.
+  void LogTCPConnectedMetrics() const;
 
   // Record histogram of time until first byte of header is received.
   void LogTransactionConnectedMetrics() const;
 
   // Record histogram of latency (durations until last byte received).
   void LogTransactionMetrics() const;
 
   // Writes a log message to help debugging in the field when we block a proxy
   // response to a CONNECT request.
   void LogBlockedTunnelResponse(int response_code) const;
@@ skipping 213 matching lines @@
   // User buffer and length passed to the Read method.
   scoped_refptr<IOBuffer> read_buf_;
   int read_buf_len_;
 
   // The time the Start method was called.
   base::Time start_time_;
 
   // The time the Connect() method was called (if it got called).
   base::Time connect_start_time_;
 
+  // The time the host resolution started (if it indeed got started).
+  base::Time host_resolution_start_time_;
+
   enum State {
     STATE_RESOLVE_PROXY,
     STATE_RESOLVE_PROXY_COMPLETE,
     STATE_INIT_CONNECTION,
     STATE_INIT_CONNECTION_COMPLETE,
     STATE_RESOLVE_HOST,
     STATE_RESOLVE_HOST_COMPLETE,
     STATE_TCP_CONNECT,
     STATE_TCP_CONNECT_COMPLETE,
     STATE_SSL_CONNECT,
     STATE_SSL_CONNECT_COMPLETE,
     STATE_WRITE_HEADERS,
     STATE_WRITE_HEADERS_COMPLETE,
     STATE_WRITE_BODY,
     STATE_WRITE_BODY_COMPLETE,
     STATE_READ_HEADERS,
     STATE_READ_HEADERS_COMPLETE,
     STATE_READ_BODY,
     STATE_READ_BODY_COMPLETE,
     STATE_DRAIN_BODY_FOR_AUTH_RESTART,
     STATE_DRAIN_BODY_FOR_AUTH_RESTART_COMPLETE,
     STATE_NONE
   };
   State next_state_;
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_NETWORK_TRANSACTION_H_