Refactor histogram_persistence to be a class.

base/metrics/histogram_samples.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.
 
 #ifndef BASE_METRICS_HISTOGRAM_SAMPLES_H_
 #define BASE_METRICS_HISTOGRAM_SAMPLES_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/atomicops.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram_base.h"
 
 namespace base {
 
 class Pickle;
 class PickleIterator;
 class SampleCountIterator;
 
 // HistogramSamples is a container storing all samples of a histogram. All
 // elements must be of a fixed width to ensure 32/64-bit interoperability.
 // If this structure changes, bump the version number for kTypeIdHistogram
-// in histogram_persistence.cc.
+// in persistent_histogram_allocator.cc.
 class BASE_EXPORT HistogramSamples {
  public:
   struct Metadata {
     // Initialized when the sample-set is first created with a value provided
     // by the caller. It is generally used to identify the sample-set across
     // threads and processes, though not necessarily uniquely as it is possible
     // to have multiple sample-sets representing subsets of the data.
     uint64_t id;
 
     // The sum of all the entries, effectivly the sum(sample * count) for
@@ skipping 76 matching lines @@
 
   // Get the index of current histogram bucket.
   // For histograms that don't use predefined buckets, it returns false.
   // Requires: !Done();
   virtual bool GetBucketIndex(size_t* index) const;
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_SAMPLES_H_