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

base/metrics/histogram_unittest.cc

Index: base/metrics/histogram_unittest.cc
diff --git a/base/metrics/histogram_unittest.cc b/base/metrics/histogram_unittest.cc
index f189267f3587affbf6624455ca0a6426cfd21ed5..e10625ee2708cf694717d9d1182f243eae861040 100644
--- a/base/metrics/histogram_unittest.cc
+++ b/base/metrics/histogram_unittest.cc
@@ -231,6 +231,31 @@ TEST_F(HistogramTest, CustomHistogramWithOnly2Buckets) {
   EXPECT_EQ(HistogramBase::kSampleType_MAX, ranges->range(2));
 }
 
+// Test the MultiAdd function.
+TEST_F(HistogramTest, MultiAddTest) {
+  const size_t kBucketCount = 50;
+  Histogram* histogram = static_cast<Histogram*>(
+      Histogram::FactoryGet("MultiAddHistogram", 10, 100, kBucketCount,
+                            HistogramBase::kNoFlags));
+
+  histogram->MultiAdd(20, 15);
+  histogram->MultiAdd(30, 14);
+
+  scoped_ptr<SampleVector> samples = histogram->SnapshotSampleVector();
+  EXPECT_EQ(29, samples->TotalCount());
+  EXPECT_EQ(15, samples->GetCount(20));
+  EXPECT_EQ(14, samples->GetCount(30));
+
+  histogram->MultiAdd(20, 25);
+  histogram->MultiAdd(30, 24);
+
+  scoped_ptr<SampleVector> samples2 = histogram->SnapshotSampleVector();
+  EXPECT_EQ(78, samples2->TotalCount());
+  EXPECT_EQ(40, samples2->GetCount(20));
+  EXPECT_EQ(38, samples2->GetCount(30));
+

[Alexei Svitkine (slow), 2015/07/31 15:39:27]

Remove entry blank lines.

[amohammadkhan, 2015/08/03 17:30:43]

Done.

+}
+
 // Make sure histogram handles out-of-bounds data gracefully.
 TEST_F(HistogramTest, BoundsTest) {
   const size_t kBucketCount = 50;