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..9c8f7656419ab666fe49e3f360d4c267792943bf 100644
--- a/base/metrics/sparse_histogram.cc
+++ b/base/metrics/sparse_histogram.cc
@@ -54,6 +54,15 @@ void SparseHistogram::Add(Sample value) {
   FindAndRunCallback(value);
 }
 
+void SparseHistogram::MultiAdd(Sample value, int repetition) {
+  {
+    base::AutoLock auto_lock(lock_);
+    samples_.Accumulate(value, repetition);
+  }
+
+  FindAndRunCallback(value);
+}
+
 scoped_ptr<HistogramSamples> SparseHistogram::SnapshotSamples() const {
   scoped_ptr<SampleMap> snapshot(new SampleMap());