Add multi_profile_user_count field to system_profile proto.

chrome/browser/metrics/metrics_log.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 file defines a set of user experience metrics data recorded by
 // the MetricsService.  This is the unit of data that is sent to the server.
 
 #ifndef CHROME_BROWSER_METRICS_METRICS_LOG_H_
 #define CHROME_BROWSER_METRICS_METRICS_LOG_H_
 
@@ skipping 166 matching lines @@
   void WriteGoogleUpdateProto(const GoogleUpdateMetrics& google_update_metrics);
 
   // Sets the Bluetooth Adapter instance used for the WriteBluetoothProto()
   // call.
   void SetBluetoothAdapter(scoped_refptr<device::BluetoothAdapter> adapter);
 
   // Writes info about paired Bluetooth devices on this system.
   // This is a no-op if called on a non-Chrome OS platform.
   void WriteBluetoothProto(metrics::SystemProfileProto::Hardware* hardware);
 
+#if defined(OS_CHROMEOS)
+  // Update the number of users logged into a multi-profile session.
+  // If the number of users change while the log is open, we invalidate

[Ilya Sherman, 2013/10/08 01:31:03]

nit: "we invalidate" -> "the call invalidates" or some other phrasing without
"we" is preferred.

[Tim Song, 2013/10/08 20:29:40]

Done.

+  // the value.
+  void UpdateMultiProfileUserCount();
+#endif
+
   // Observes network state to provide values for SystemProfile::Network.
   MetricsNetworkObserver network_observer_;
 
 #if defined(OS_CHROMEOS)
   metrics::PerfProvider perf_provider_;
 #endif
 
   // Bluetooth Adapter instance for collecting information about paired devices.
   scoped_refptr<device::BluetoothAdapter> adapter_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsLog);
 };
 
 #endif  // CHROME_BROWSER_METRICS_METRICS_LOG_H_