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

base/metrics/histogram_base.h

Index: base/metrics/histogram_base.h
diff --git a/base/metrics/histogram_base.h b/base/metrics/histogram_base.h
index 1bc1f6eb6fe78bf4a48576f60e3da694a74da932..684c7040d85ecd59e333e79743e14591381f3bd0 100644
--- a/base/metrics/histogram_base.h
+++ b/base/metrics/histogram_base.h
@@ -121,6 +121,11 @@ class BASE_EXPORT HistogramBase {
 
   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);