Call StatisticsRecorder::Initialize in GlobalHistogramAllocator's ctor

base/metrics/persistent_histogram_allocator.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/metrics/persistent_histogram_allocator.h"
 
 #include <memory>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
@@ skipping 879 matching lines @@
   // be open elsewhere. Open handles will continue to operate normally but
   // new opens will not be possible.
   File file(persistent_location_,
             File::FLAG_OPEN | File::FLAG_READ | File::FLAG_DELETE_ON_CLOSE);
 #endif
 }
 
 GlobalHistogramAllocator::GlobalHistogramAllocator(
     std::unique_ptr<PersistentMemoryAllocator> memory)
     : PersistentHistogramAllocator(std::move(memory)),
-      import_iterator_(this) {}
+      import_iterator_(this) {
+  StatisticsRecorder::Initialize();

[bcwhite, 2016/09/21 19:35:11]

Let's add a comment:

Make sure the StatisticsRecorder is initialized to prevent duplicate
histograms from being created. It's safe to call this multiple times.

[scottmg, 2016/09/21 19:37:56]

Done.

+}
 
 void GlobalHistogramAllocator::ImportHistogramsToStatisticsRecorder() {
   // Skip the import if it's the histogram that was last created. Should a
   // race condition cause the "last created" to be overwritten before it
   // is recognized here then the histogram will be created and be ignored
   // when it is detected as a duplicate by the statistics-recorder. This
   // simple check reduces the time of creating persistent histograms by
   // about 40%.
   Reference record_to_ignore = last_created();
 
   // There is no lock on this because the iterator is lock-free while still
   // guaranteed to only return each entry only once. The StatisticsRecorder
   // has its own lock so the Register operation is safe.
   while (true) {
     std::unique_ptr<HistogramBase> histogram =
         import_iterator_.GetNextWithIgnore(record_to_ignore);
     if (!histogram)
       break;
     StatisticsRecorder::RegisterOrDeleteDuplicate(histogram.release());
   }
 }
 
 }  // namespace base