Log histograms on shutdown when verbose logging is on

base/metrics/statistics_recorder.cc

Index: base/metrics/statistics_recorder.cc
diff --git a/base/metrics/statistics_recorder.cc b/base/metrics/statistics_recorder.cc
index d0fa2add3603b3f574dfa9ef9e5ee2e6b152aafc..8959472bb83904c56fee4ce80fc7a2b8f7b03d6f 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -22,6 +22,8 @@ namespace {
 base::LazyInstance<base::StatisticsRecorder>::Leaky g_statistics_recorder_ =
     LAZY_INSTANCE_INITIALIZER;
 
+bool g_vlog_initialized = false;

[Alexei Svitkine (slow), 2016/04/14 20:47:39]

Can this just be a member of the StatisticsRecorder?

+
 bool HistogramNameLesser(const base::HistogramBase* a,
                          const base::HistogramBase* b) {
   return a->histogram_name() < b->histogram_name();
@@ -298,6 +300,19 @@ StatisticsRecorder::HistogramIterator StatisticsRecorder::end() {
 }
 
 // static
+void StatisticsRecorder::InitLogOnShutdown() {
+  if (lock_ == nullptr)
+    return;
+  base::AutoLock auto_lock(*lock_);
+  g_statistics_recorder_.Get().InitLogOnShutdownWithoutLock();
+}
+
+// static
+bool StatisticsRecorder::VLogInitializedForTesting() {
+  return g_vlog_initialized;
+}
+
+// static
 void StatisticsRecorder::GetSnapshot(const std::string& query,
                                      Histograms* snapshot) {
   if (lock_ == NULL)
@@ -399,8 +414,7 @@ StatisticsRecorder::StatisticsRecorder() {
   callbacks_ = new CallbackMap;
   ranges_ = new RangesMap;
 
-  if (VLOG_IS_ON(1))
-    AtExitManager::RegisterCallback(&DumpHistogramsToVlog, this);
+  InitLogOnShutdownWithoutLock();
 }
 
 StatisticsRecorder::~StatisticsRecorder() {
@@ -410,6 +424,13 @@ StatisticsRecorder::~StatisticsRecorder() {
   Reset();
 }
 
+void StatisticsRecorder::InitLogOnShutdownWithoutLock() {
+  if (!g_vlog_initialized && VLOG_IS_ON(1)) {
+    g_vlog_initialized = true;
+    AtExitManager::RegisterCallback(&DumpHistogramsToVlog, this);
+  }
+}
+
 // static
 void StatisticsRecorder::Reset() {
   // If there's no lock then there is nothing to reset.