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

base/metrics/sparse_histogram.cc

Index: base/metrics/sparse_histogram.cc
diff --git a/base/metrics/sparse_histogram.cc b/base/metrics/sparse_histogram.cc
index a853dce3505f450c5ef814371f63f1fa92e7523f..9abced007a3977d5a4c3af3caa4393eb28a9f6df 100644
--- a/base/metrics/sparse_histogram.cc
+++ b/base/metrics/sparse_histogram.cc
@@ -46,11 +46,17 @@ bool SparseHistogram::HasConstructionArguments(
 }
 
 void SparseHistogram::Add(Sample value) {
+  AddCount(value, 1);
+}
+
+void SparseHistogram::AddCount(Sample value, int count) {
   {
     base::AutoLock auto_lock(lock_);
-    samples_.Accumulate(value, 1);
+    if (count < 0) {

[Alexei Svitkine (slow), 2015/08/03 18:15:42]

Same comment as in the other method. This if can probably be at the start of the
method, before the lock.

[amohammadkhan, 2015/08/04 18:22:51]

Done.

+      count = 0;
+    }
+    samples_.Accumulate(value, count);
   }
-

[Alexei Svitkine (slow), 2015/08/03 18:15:42]

Nit: Keep the empty line.

[amohammadkhan, 2015/08/04 18:22:51]

Done.

   FindAndRunCallback(value);
 }