Remove unnecessary lock that causes reentry.

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 b19a897a96c1ab6e2d7737bd2648100c9bd10281..627b5d195c71f1eeea73287bbfb8b3a9123fe440 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -285,9 +285,6 @@ void StatisticsRecorder::GetBucketRanges(
 HistogramBase* StatisticsRecorder::FindHistogram(base::StringPiece name) {
   if (lock_ == NULL)
     return NULL;
-  base::AutoLock auto_lock(*lock_);
-  if (histograms_ == NULL)
-    return NULL;
 
   // Import histograms from known persistent storage. Histograms could have
   // been added by other processes and they must be fetched and recognized
@@ -297,6 +294,10 @@ HistogramBase* StatisticsRecorder::FindHistogram(base::StringPiece name) {
   if (allocator)
     allocator->ImportHistogramsToStatisticsRecorder();
 
+  base::AutoLock auto_lock(*lock_);

[Alexei Svitkine (slow), 2016/04/08 14:51:48]

Add a comment for why this is done here and not at the top.

[bcwhite, 2016/04/08 15:06:08]

Done.

+  if (histograms_ == NULL)
+    return NULL;
+
   HistogramMap::iterator it = histograms_->find(name);
   if (histograms_->end() == it)
     return NULL;