Fix HistogramTester::GetAllSamples when empty.

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 051f599f45a360f7afc31f897c051260a34fecde..09b4ef30ee3aa6863014db96e136b11b7274ca30 100644
--- a/base/test/histogram_tester.cc
+++ b/base/test/histogram_tester.cc
@@ -79,11 +79,13 @@ std::vector<Bucket> HistogramTester::GetAllSamples(
   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;
 }