Don't crash in StatisticsRecorder if VLOG level changes.

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 "base/at_exit.h"
 #include "base/debug/leak_annotations.h"
 #include "base/json/string_escape.h"
 #include "base/logging.h"
@@ skipping 268 matching lines @@
   base::AutoLock auto_lock(*lock_);
   histograms_ = new HistogramMap;
   ranges_ = new RangesMap;
 
   if (VLOG_IS_ON(1))
     AtExitManager::RegisterCallback(&DumpHistogramsToVlog, this);
 }
 
 // static
 void StatisticsRecorder::DumpHistogramsToVlog(void* instance) {
-  DCHECK(VLOG_IS_ON(1));
+  if (!VLOG_IS_ON(1))
+    return;

[Ilya Sherman, 2015/05/12 20:18:34]

I think we can just remove this check.  The function is only registered as a
callback when vlog is on at construction time, so in normal operation there's no
way to hit this path.

Alternately, you could remove the check on line 283.

 
   string output;
   StatisticsRecorder::WriteGraph(std::string(), &output);
   VLOG(1) << output;
 }
 
 StatisticsRecorder::~StatisticsRecorder() {
   DCHECK(histograms_ && ranges_ && lock_);
 
   // Clean up.
@@ skipping 13 matching lines @@
 
 
 // static
 StatisticsRecorder::HistogramMap* StatisticsRecorder::histograms_ = NULL;
 // static
 StatisticsRecorder::RangesMap* StatisticsRecorder::ranges_ = NULL;
 // static
 base::Lock* StatisticsRecorder::lock_ = NULL;
 
 }  // namespace base