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

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index 7ff1b16184f10c9e54dd501b1b95a1f34fefc253..41383f9ddc9fab4cfba0f966614ad4ff716890b1 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -284,6 +284,20 @@ void Histogram::Add(int value) {
   FindAndRunCallback(value);
 }
 
+void Histogram::MultiAdd(int value, int repetition) {
+  DCHECK_EQ(0, ranges(0));
+  DCHECK_EQ(kSampleType_MAX, ranges(bucket_count()));
+
+  if (value > kSampleType_MAX - 1)
+    value = kSampleType_MAX - 1;
+  if (value < 0)
+    value = 0;
+  samples_->Accumulate(value, repetition);
+
+  FindAndRunCallback(value);
+
+}
+
 scoped_ptr<HistogramSamples> Histogram::SnapshotSamples() const {
   return SnapshotSampleVector().Pass();
 }