Call StatisticsRecorder::Initialize when a GlobalHistogramAllocator is created.

base/metrics/statistics_recorder.cc

 // Copyright (c) 2012 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/statistics_recorder.h"
 
 #include <memory>
 
 #include "base/at_exit.h"
 #include "base/debug/leak_annotations.h"
@@ skipping 75 matching lines @@
   // Clean out what this object created and then restore what existed before.
   Reset();
   base::AutoLock auto_lock(*lock_);
   histograms_ = existing_histograms_.release();
   callbacks_ = existing_callbacks_.release();
   ranges_ = existing_ranges_.release();
 }
 
 // static
 void StatisticsRecorder::Initialize() {
+  // Tests sometimes create local StatisticsRecorders in order to provide a
+  // contained environment of histograms that can be later discarded. If a
+  // true global instance gets created in this environment then it will
+  // eventually get disconnected when the local instance destructs and
+  // restores the previous state, resulting in no StatisticsRecorder at all.
+  // The global lazy instance, however, will remain valid thus ensuring that
+  // another never gets installed via this method. If a |histograms_| map
+  // exists then assume the StatisticsRecorder is already "initialized".
+  if (histograms_)
+    return;
+
   // Ensure that an instance of the StatisticsRecorder object is created.
   g_statistics_recorder_.Get();
 }
 
 // static
 bool StatisticsRecorder::IsActive() {
   if (lock_ == NULL)
     return false;
   base::AutoLock auto_lock(*lock_);
   return NULL != histograms_;
@@ skipping 428 matching lines @@
 // static
 StatisticsRecorder::HistogramMap* StatisticsRecorder::histograms_ = NULL;
 // static
 StatisticsRecorder::CallbackMap* StatisticsRecorder::callbacks_ = NULL;
 // static
 StatisticsRecorder::RangesMap* StatisticsRecorder::ranges_ = NULL;
 // static
 base::Lock* StatisticsRecorder::lock_ = NULL;
 
 }  // namespace base