Fix HistogramTester::GetAllSamples when empty.

base/test/histogram_tester.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/test/histogram_tester.h"
 
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/metrics/sample_map.h"
 #include "base/metrics/statistics_recorder.h"
@@ skipping 61 matching lines @@
     // No histogram means there were zero samples.
     EXPECT_EQ(count, 0) << "Histogram \"" << name << "\" does not exist.";
   }
 }
 
 std::vector<Bucket> HistogramTester::GetAllSamples(
     const std::string& name) const {
   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));
+  if (snapshot) {

[Ilya Sherman, 2015/08/07 17:20:12]

optional nit: I'd write this as an early return, personally

[twifkak, 2015/08/07 19:36:38]

Hmm. Was going to do this, but on second thought, requires duplicating the
return parameter. Kind of a nit-on-a-nit, I know.

+    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;
 }
 
 HistogramTester::CountsMap HistogramTester::GetTotalCountsForPrefix(
     const std::string& query) const {
   EXPECT_TRUE(query.find('.') != std::string::npos)
       << "|query| ought to contain at least one period, to avoid matching too"
       << " many histograms.";
 
@@ skipping 67 matching lines @@
 
 bool Bucket::operator==(const Bucket& other) const {
   return min == other.min && count == other.count;
 }
 
 void PrintTo(const Bucket& bucket, std::ostream* os) {
   *os << "Bucket " << bucket.min << ": " << bucket.count;
 }
 
 }  // namespace base