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..404a6554a0a237d3289a0bd9e7c5f60d82e4f69e 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -285,18 +285,22 @@ 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
   // locally. If the persistent memory segment is not shared between processes,
   // this call does nothing.
+  // This must be called *before* the lock is acquired below because it will
+  // call back into this object to register histograms. Those called methods
+  // will acquire the lock at that time.
   GlobalHistogramAllocator* allocator = GlobalHistogramAllocator::Get();
   if (allocator)
     allocator->ImportHistogramsToStatisticsRecorder();
 
+  base::AutoLock auto_lock(*lock_);
+  if (histograms_ == NULL)
+    return NULL;
+
   HistogramMap::iterator it = histograms_->find(name);
   if (histograms_->end() == it)
     return NULL;