Serialize/Deserialize support in HistogramBase

chrome/common/metrics/metrics_log_base.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_COMMON_METRICS_METRICS_LOG_BASE_H_
 #define CHROME_COMMON_METRICS_METRICS_LOG_BASE_H_
 
@@ skipping 57 matching lines @@
   // url - which URL was loaded
   // origin - what kind of action initiated the load
   // load_time - how long it took to load the page
   void RecordLoadEvent(int window_id,
                        const GURL& url,
                        content::PageTransition origin,
                        int session_index,
                        base::TimeDelta load_time);
 
   // Record any changes in a given histogram for transmission.
-  void RecordHistogramDelta(const base::Histogram& histogram,
+  void RecordHistogramDelta(const std::string& histogram_name,
                             const base::HistogramSamples& snapshot);
 
   // Stop writing to this record and generate the encoded representation.
   // None of the Record* methods can be called after this is called.
   void CloseLog();
 
   // These methods allow retrieval of the encoded representation of the
   // record.  They can only be called after CloseLog() has been called.
   // GetEncodedLog returns false if buffer_size is less than
   // GetEncodedLogSize();
@@ skipping 88 matching lines @@
   // Isolated to limit the dependency on the XML library for our consumers.
   XmlWrapper* xml_wrapper_;
 
   // Stores the protocol buffer representation for this log.
   metrics::ChromeUserMetricsExtension uma_proto_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsLogBase);
 };
 
 #endif  // CHROME_COMMON_METRICS_METRICS_LOG_BASE_H_