Adding UseCounter specific for extensions

base/test/histogram_tester.cc

Index: base/test/histogram_tester.cc
diff --git a/base/test/histogram_tester.cc b/base/test/histogram_tester.cc
index 5ca3c2fe9e8dd6145f05741fdf6022be49e877e0..cdc67bc121e5ff33cf80df1898bc396a91ba4624 100644
--- a/base/test/histogram_tester.cc
+++ b/base/test/histogram_tester.cc
@@ -61,6 +61,21 @@ void HistogramTester::ExpectBucketCount(
   }
 }
 
+void HistogramTester::ExpectTotalCountExcept(const std::string& name,

[Nico, 2017/05/09 19:36:45]

Move this below ExpectTotalCount() so order in cc matches order in h file

[lunalu1, 2017/05/10 19:39:38]

Done.

+                                             HistogramBase::Sample sample,
+                                             HistogramBase::Count count) const {
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
+  EXPECT_NE(nullptr, histogram)
+      << "Histogram \"" << name << "\" does not exist.";
+  if (histogram) {
+    std::unique_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
+    CheckTotalCountExcept(name, sample, count, *samples);
+  } else {
+    // No histogram means there were zero samples.
+    EXPECT_EQ(count, 0) << "Histogram \"" << name << "\" does not exist.";
+  }
+}
+
 void HistogramTester::ExpectTotalCount(const std::string& name,
                                        HistogramBase::Count count) const {
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
@@ -173,6 +188,27 @@ void HistogramTester::CheckTotalCount(const std::string& name,
       << expected_count << "). It has (" << actual_count << ").";
 }
 
+void HistogramTester::CheckTotalCountExcept(

[Nico, 2017/05/09 19:36:45]

The new code in this file looks pretty similar to already-existing code in this
file. Alexei, do you have a good idea how we could share more code here?

[lunalu1, 2017/05/10 19:39:38]

IMHO, we can implement getters (privately if we don't want to expose them and
call shared getters in Exepect* and Check*). WDYT?

+    const std::string& name,
+    HistogramBase::Sample sample,
+    HistogramBase::Count expected_count,
+    const HistogramSamples& samples) const {
+  int actual_total_count = samples.TotalCount();
+  int actual_bucket_count = samples.GetCount(sample);
+
+  auto histogram_data = histograms_snapshot_.find(name);
+  if (histogram_data != histograms_snapshot_.end()) {
+    actual_total_count -= histogram_data->second->TotalCount();
+    actual_bucket_count -= histogram_data->second->GetCount(sample);
+  }
+  int actual_count = actual_total_count - actual_bucket_count;
+
+  EXPECT_EQ(expected_count, actual_count)
+      << "Histogram \"" << name
+      << "\" does not have the right total number of samples ("
+      << expected_count << "). It has (" << actual_count << ").";
+}
+
 bool Bucket::operator==(const Bucket& other) const {
   return min == other.min && count == other.count;
 }