Add UMA Histogram Manager to Cronet.

components/metrics/metrics_log.h

 // Copyright 2014 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 COMPONENTS_METRICS_METRICS_LOG_H_
 #define COMPONENTS_METRICS_METRICS_LOG_H_
 
@@ skipping 123 matching lines @@
     return creation_time_;
   }
 
   int num_events() const {
     return uma_proto_.omnibox_event_size() +
            uma_proto_.user_action_event_size();
   }
 
   LogType log_type() const { return log_type_; }
 
+  ChromeUserMetricsExtension* uma_proto() { return &uma_proto_; }
+
  protected:
   // Exposed for the sake of mocking/accessing in test code.
 
   // Fills |field_trial_ids| with the list of initialized field trials name and
   // group ids.
   virtual void GetFieldTrialIds(
       std::vector<variations::ActiveGroupId>* field_trial_ids) const;
 
-  ChromeUserMetricsExtension* uma_proto() { return &uma_proto_; }
   const ChromeUserMetricsExtension* uma_proto() const {
     return &uma_proto_;
   }
 
  private:
   // Returns true if the environment has already been filled in by a call to
   // RecordEnvironment() or LoadSavedEnvironmentFromPrefs().
   bool HasEnvironment() const;
 
   // Returns true if the stability metrics have already been filled in by a
@@ skipping 29 matching lines @@
   const base::TimeTicks creation_time_;
 
   PrefService* local_state_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsLog);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_METRICS_LOG_H_