Add ThreadChecker to HistogramSnapshotManager.

base/metrics/histogram_snapshot_manager.h

 // 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.
 
 #ifndef BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_
 #define BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_
 
 #include <stdint.h>
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/metrics/histogram_base.h"
+#include "base/threading/thread_checker.h"
 
 namespace base {
 
 class HistogramSamples;
 class HistogramFlattener;
 
 // HistogramSnapshotManager handles the logistics of gathering up available
 // histograms for recording either to disk or for transmission (such as from
 // renderer to browser, or from browser to UMA upload). Since histograms can sit
 // in memory for an extended period of time, and are vulnerable to memory
@@ skipping 44 matching lines @@
   };
 
   // Capture and hold samples from a histogram. This does all the heavy
   // lifting for PrepareDelta() and PrepareAbsolute().
   void PrepareSamples(const HistogramBase* histogram,
                       std::unique_ptr<HistogramSamples> samples);
 
   // Try to detect and fix count inconsistency of logged samples.
   void InspectLoggedSamplesInconsistency(
       const HistogramSamples& new_snapshot,
       HistogramSamples* logged_samples);

[Alexei Svitkine (slow), 2017/04/24 19:29:07]

Remove this too. :)

[bcwhite, 2017/04/24 19:43:05]

Oops.  Didn't save the file.  :-)

 
   // For histograms, track what has been previously seen, indexed
   // by the hash of the histogram name.
   std::map<uint64_t, SampleInfo> known_histograms_;
 
   // |histogram_flattener_| handles the logistics of recording the histogram
   // deltas.
   HistogramFlattener* histogram_flattener_;  // Weak.
 
+  ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(HistogramSnapshotManager);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_SNAPSHOT_MANAGER_H_