Record device scale factor in the metrics log

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 108 matching lines @@
 
  protected:
   // Exposed for the sake of mocking in test code.
 
   // Returns the PrefService from which to log metrics data.
   virtual PrefService* GetPrefService();
 
   // Returns the screen size for the primary monitor.
   virtual gfx::Size GetScreenSize() const;
 
+  // Returns the device scale factor for the primary monitor.
+  virtual float GetScreenDeviceScaleFactor() const;
+
   // Returns the number of monitors the user is using.
   virtual int GetScreenCount() const;
 
   // Fills |field_trial_ids| with the list of initialized field trials name and
   // group ids.
   virtual void GetFieldTrialIds(
     std::vector<chrome_variations::SelectedGroupId>* field_trial_ids) const;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(MetricsLogTest, ChromeOSStabilityData);
@@ skipping 38 matching lines @@
                            const base::DictionaryValue& profile_metrics);
 
   // Writes info about the Google Update install that is managing this client.
   // This is a no-op if called on a non-Windows platform.
   void WriteGoogleUpdateProto(const GoogleUpdateMetrics& google_update_metrics);
 
   DISALLOW_COPY_AND_ASSIGN(MetricsLog);
 };
 
 #endif  // CHROME_BROWSER_METRICS_METRICS_LOG_H_