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..2e89a2cc3501b9ff43c8129a75c994d8b7a6a640 100644
--- a/base/test/histogram_tester.cc
+++ b/base/test/histogram_tester.cc
@@ -73,6 +73,19 @@ void HistogramTester::ExpectTotalCount(const std::string& name,
   }
 }
 
+std::vector<Bucket> HistogramTester::GetAllSamples(const std::string& name) {
+  std::vector<Bucket> 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(Bucket(sample, count));
+  }
+  return samples;
+}
+
 scoped_ptr<HistogramSamples> HistogramTester::GetHistogramSamplesSinceCreation(
     const std::string& histogram_name) {
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(histogram_name);
@@ -120,4 +133,13 @@ void HistogramTester::CheckTotalCount(
       << expected_count << "). It has (" << actual_count << ").";
 }
 
+bool Bucket::operator==(const Bucket& other) const {
+  return min_ == other.min_ && count_ == other.count_;
+}
+
+void PrintTo(const Bucket& bucket, std::ostream* os) {
+  *os << bucket.count_ << (bucket.count_ == 1 ? " sample " : " samples ")
+      << "in bucket " << bucket.min_;

[Ilya Sherman, 2015/06/27 07:25:19]

WDYT of something shorter, like the following?

  *os << bucket.min << ": " << bucket.count;  // e.g. "1: 4"

I'm not really sure -- that might be too dense, and not much clearer than a
pair.  I guess I'm trying to find something a little denser, without being so
dense as to be confusing.

[twifkak, 2015/06/29 21:52:29]

That doesn't seem to be any clearer than a pair. However, I was bothered by the
fact that it was output in reverse order to the constructor args. How about
this?

[Ilya Sherman, 2015/06/29 22:05:34]

Yeah, I think that's a good compromise between clarity and density.  Thanks!

+}
+
 }  // namespace base