Report histogram creation results.

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..52e005dace06a891b3be363f1a15c9282da9b944 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -67,6 +67,13 @@ StatisticsRecorder::HistogramIterator::operator++() {
   return *this;
 }
 
+StatisticsRecorder::~StatisticsRecorder() {
+  DCHECK(histograms_ && ranges_ && lock_);

[Alexei Svitkine (slow), 2016/03/07 21:14:51]

Nit: Not sure why I missed that in the previous CL, but these should be separate
DCHECKs so that if it fails, it's clear which one it is.

[bcwhite, 2016/03/07 22:20:41]

Done.

+
+  // Global clean up.
+  Reset();
+}
+
 // static
 void StatisticsRecorder::Initialize() {
   // Ensure that an instance of the StatisticsRecorder object is created.
@@ -369,6 +376,17 @@ StatisticsRecorder::OnSampleCallback StatisticsRecorder::FindCallback(
 }
 
 // static
+size_t StatisticsRecorder::GetHistogramCount() {
+  if (!lock_)
+    return 0;
+
+  base::AutoLock auto_lock(*lock_);
+  if (!histograms_)
+    return 0;
+  return histograms_->size();
+}
+
+// static
 void StatisticsRecorder::ResetForTesting() {
   // Just call the private version that is used also by the destructor.
   Reset();
@@ -403,13 +421,6 @@ StatisticsRecorder::StatisticsRecorder() {
     AtExitManager::RegisterCallback(&DumpHistogramsToVlog, this);
 }
 
-StatisticsRecorder::~StatisticsRecorder() {
-  DCHECK(histograms_ && ranges_ && lock_);
-
-  // Global clean up.
-  Reset();
-}
-
 // static
 void StatisticsRecorder::Reset() {
   // If there's no lock then there is nothing to reset.