Log histograms on shutdown when verbose logging is on

base/metrics/statistics_recorder.h

Index: base/metrics/statistics_recorder.h
diff --git a/base/metrics/statistics_recorder.h b/base/metrics/statistics_recorder.h
index 002758e840e1aa404409e6a14785615e790c9ce5..8dfa44e363ef4c4b4d0913aa296f65dd8fb1da83 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -167,6 +167,12 @@ class BASE_EXPORT StatisticsRecorder {
   // Returns the number of known histograms.
   static size_t GetHistogramCount();
 
+  // Initializes logging histograms with --v=1. Safe to call several times.

[Lei Zhang, 2016/07/04 21:03:31]

s/several/multiple/

+  // Is called from ctor but for browser it seems that it is more useful to
+  // start logging after statistics recorder, so we need to init log-on-shutdown
+  // later.
+  static void InitLogOnShutdown();
+
   // Removes a histogram from the internal set of known ones. This can be
   // necessary during testing persistent histograms where the underlying
   // memory is being released.
@@ -195,6 +201,7 @@ class BASE_EXPORT StatisticsRecorder {
   typedef std::map<uint32_t, std::list<const BucketRanges*>*> RangesMap;
 
   friend struct DefaultLazyInstanceTraits<StatisticsRecorder>;
+  friend class StatisticsRecorderTest;
 
   // Imports histograms from global persistent memory. The global lock must
   // not be held during this call.
@@ -205,6 +212,10 @@ class BASE_EXPORT StatisticsRecorder {
   // call the constructor to get a clean StatisticsRecorder.
   StatisticsRecorder();
 
+  // Initialize implementation but without lock. Caller should guard
+  // StatisticsRecorder by itlsef if needed (it isn't in unit tests).

[Lei Zhang, 2016/07/04 21:03:31]

type: "itself"

+  void InitLogOnShutdownWithoutLock();
+
   // These are copies of everything that existed when the (test) Statistics-
   // Recorder was created. The global ones have to be moved aside to create a
   // clean environment.
@@ -212,6 +223,8 @@ class BASE_EXPORT StatisticsRecorder {
   std::unique_ptr<CallbackMap> existing_callbacks_;
   std::unique_ptr<RangesMap> existing_ranges_;
 
+  bool vlog_initialized_ = false;
+
   static void Reset();
   static void DumpHistogramsToVlog(void* instance);