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..fb9ca9d4473d8e1c7b2811bcf3edae5c13c47e67 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -271,17 +271,28 @@ bool Histogram::HasConstructionArguments(Sample expected_minimum,
           (expected_bucket_count == bucket_count()));
 }
 
+int ClampValue(int value) {

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

Put this in the anon namespace at the top of the file. Add a comment.

Alternatively, since you're making Add() call AddCount() now, maybe just keep
this inside the method like before instead of a separate helper.

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

Done.

+  if (value > Histogram::kSampleType_MAX - 1)
+    return Histogram::kSampleType_MAX - 1;
+  if (value < 0)
+    return 0;
+  return value;
+}
+
 void Histogram::Add(int value) {
+  AddCount(value, 1);
+}
+
+void Histogram::AddCount(int value, int count) {
   DCHECK_EQ(0, ranges(0));
   DCHECK_EQ(kSampleType_MAX, ranges(bucket_count()));
+  if (count < 0) {

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

If the body is a single line, no need for {}'s.

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

Done.

+    count = 0;

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

Seems like a count of 0 would actually not change anything. Suggesting change if
to be <= 0 and then doing a return with a NOTREACHED() inside it.

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

Done.

+  }
+  int clamped_value = ClampValue(value);
+  samples_->Accumulate(clamped_value, count);
 
-  if (value > kSampleType_MAX - 1)
-    value = kSampleType_MAX - 1;
-  if (value < 0)
-    value = 0;
-  samples_->Accumulate(value, 1);
-
-  FindAndRunCallback(value);
+  FindAndRunCallback(clamped_value);
 }
 
 scoped_ptr<HistogramSamples> Histogram::SnapshotSamples() const {