Add SampleMap and use it in SparseHistogram

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 "base/basictypes.h"
 #include "base/metrics/histogram_base.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 24 matching lines @@
   virtual void Subtract(const HistogramSamples& other);
 
   virtual scoped_ptr<SampleCountIterator> Iterator() const = 0;
   virtual bool Serialize(Pickle* pickle) const;
 
   // Accessor fuctions.
   int64 sum() const { return sum_; }
   HistogramBase::Count redundant_count() const { return redundant_count_; }
 
  protected:
-  // Based on |instruction| type, add or subtract sample counts data from the
-  // iterator.
-  enum Instruction { ADD, SUBTRACT };
-  virtual bool AddSubtractImpl(SampleCountIterator* iter,
-                               Instruction instruction) = 0;
+  // Based on |op| type, add or subtract sample counts data from the iterator.
+  enum Operator { ADD, SUBTRACT };
+  virtual bool AddSubtractImpl(SampleCountIterator* iter, Operator op) = 0;
 
   void IncreaseSum(int64 diff);
   void IncreaseRedundantCount(HistogramBase::Count diff);
 
  private:
   int64 sum_;
 
   // |redundant_count_| helps identify memory corruption. It redundantly stores
   // the total number of samples accumulated in the histogram. We can compare
   // this count to the sum of the counts (TotalCount() function), and detect
@@ skipping 20 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_