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

base/metrics/histogram.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.
 
 // Histogram is an object that aggregates statistics, and can summarize them in
 // various forms, including ASCII graphical, HTML, and numerically (as a
 // vector of numbers corresponding to each of the aggregating buckets).
 
 // It supports calls to accumulate either time intervals (which are processed
 // as integral number of milliseconds), or arbitrary integral units.
@@ skipping 163 matching lines @@
                                            Sample* minimum,
                                            Sample* maximum,
                                            size_t* bucket_count);
 
   // HistogramBase implementation:
   HistogramType GetHistogramType() const override;
   bool HasConstructionArguments(Sample expected_minimum,
                                 Sample expected_maximum,
                                 size_t expected_bucket_count) const override;
   void Add(Sample value) override;
+  void AddCount(Sample value, int count) override;
   scoped_ptr<HistogramSamples> SnapshotSamples() const override;
   void AddSamples(const HistogramSamples& samples) override;
   bool AddSamplesFromPickle(base::PickleIterator* iter) override;
   void WriteHTMLGraph(std::string* output) const override;
   void WriteAscii(std::string* output) const override;
 
  protected:
   // |ranges| should contain the underflow and overflow buckets. See top
   // comments for example.
   Histogram(const std::string& name,
@@ skipping 17 matching lines @@
   // be a name (or string description) given to the bucket.
   virtual const std::string GetAsciiBucketRange(size_t it) const;
 
  private:
   // Allow tests to corrupt our innards for testing purposes.
   FRIEND_TEST_ALL_PREFIXES(HistogramTest, BoundsTest);
   FRIEND_TEST_ALL_PREFIXES(HistogramTest, BucketPlacementTest);
   FRIEND_TEST_ALL_PREFIXES(HistogramTest, CorruptBucketBounds);
   FRIEND_TEST_ALL_PREFIXES(HistogramTest, CorruptSampleCounts);
   FRIEND_TEST_ALL_PREFIXES(HistogramTest, NameMatchTest);
+  FRIEND_TEST_ALL_PREFIXES(HistogramTest, AddCountTest);
 
   friend class StatisticsRecorder;  // To allow it to delete duplicates.
   friend class StatisticsRecorderTest;
 
   friend BASE_EXPORT_PRIVATE HistogramBase* DeserializeHistogramInfo(
       base::PickleIterator* iter);
   static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
 
   // Implementation of SnapshotSamples function.
   scoped_ptr<SampleVector> SnapshotSampleVector() const;
@@ skipping 201 matching lines @@
   static bool ValidateCustomRanges(const std::vector<Sample>& custom_ranges);
   static BucketRanges* CreateBucketRangesFromCustomRanges(
       const std::vector<Sample>& custom_ranges);
 
   DISALLOW_COPY_AND_ASSIGN(CustomHistogram);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_H_