Add HistogramTester::GetAllSamples.

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 ea738b0557b6e864a7e68c7d840c079d5c5967d8..7529af1d057b64aada5ece31d03c4d5082738321 100644
--- a/base/test/histogram_tester.cc
+++ b/base/test/histogram_tester.cc
@@ -73,6 +73,20 @@ void HistogramTester::ExpectTotalCount(const std::string& name,
   }
 }
 
+std::vector<std::pair<HistogramBase::Sample, HistogramBase::Count>>
+HistogramTester::GetAllSamples(const std::string& name) {
+  std::vector<std::pair<HistogramBase::Sample, HistogramBase::Count>> samples;
+  scoped_ptr<HistogramSamples> snapshot =
+      GetHistogramSamplesSinceCreation(name);
+  for (auto it = snapshot->Iterator(); !it->Done(); it->Next()) {
+    HistogramBase::Sample sample;
+    HistogramBase::Count count;
+    it->Get(&sample, nullptr, &count);
+    samples.push_back(std::make_pair(sample, count));
+  }
+  return samples;
+}
+
 scoped_ptr<HistogramSamples> HistogramTester::GetHistogramSamplesSinceCreation(
     const std::string& histogram_name) {
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(histogram_name);