Add support to increase a UMA histogram bucket by an aribitrary integer.

base/metrics/histogram_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.
 
 #ifndef BASE_METRICS_HISTOGRAM_BASE_H_
 #define BASE_METRICS_HISTOGRAM_BASE_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 103 matching lines @@
 
   // Whether the histogram has construction arguments as parameters specified.
   // For histograms that don't have the concept of minimum, maximum or
   // bucket_count, this function always returns false.
   virtual bool HasConstructionArguments(Sample expected_minimum,
                                         Sample expected_maximum,
                                         size_t expected_bucket_count) const = 0;
 
   virtual void Add(Sample value) = 0;
 
+  // In Add function the |value| bucket is increased by one, but in some use
+  // cases we need to increase this value by an arbitrary integer. AddCount
+  // function increases the |value| bucket by |count|.

[Alexei Svitkine (slow), 2015/08/04 18:25:12]

Mention that the |count| param must be > 0.

+  virtual void AddCount(Sample value, int count) = 0;
+
   // 2 convenient functions that call Add(Sample).
   void AddTime(const TimeDelta& time);
   void AddBoolean(bool value);
 
   virtual void AddSamples(const HistogramSamples& samples) = 0;
   virtual bool AddSamplesFromPickle(base::PickleIterator* iter) = 0;
 
   // Serialize the histogram info into |pickle|.
   // Note: This only serializes the construction arguments of the histogram, but
   // does not serialize the samples.
@@ skipping 51 matching lines @@
  private:
   const std::string histogram_name_;
   int32_t flags_;
 
   DISALLOW_COPY_AND_ASSIGN(HistogramBase);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_BASE_H_