Add ThreadChecker to HistogramSnapshotManager.

base/metrics/histogram_snapshot_manager.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/histogram_snapshot_manager.h"
 
 #include <memory>
 
 #include "base/debug/alias.h"
 #include "base/metrics/histogram_flattener.h"
@@ skipping 17 matching lines @@
 }
 
 void HistogramSnapshotManager::PrepareFinalDelta(
     const HistogramBase* histogram) {
   PrepareSamples(histogram, histogram->SnapshotFinalDelta());
 }
 
 void HistogramSnapshotManager::PrepareSamples(
     const HistogramBase* histogram,
     std::unique_ptr<HistogramSamples> samples) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(histogram_flattener_);
 
   // Get information known about this histogram. If it did not previously
   // exist, one will be created and initialized.
   SampleInfo* sample_info = &known_histograms_[histogram->name_hash()];
 
   // Crash if we detect that our histograms have been overwritten.  This may be
   // a fair distance from the memory smasher, but we hope to correlate these
   // crashes with other events, such as plugins, or usage patterns, etc.
   uint32_t corruption = histogram->FindCorruption(*samples);
@@ skipping 38 matching lines @@
     sample_info->inconsistencies |= corruption;
     histogram_flattener_->UniqueInconsistencyDetected(
         static_cast<HistogramBase::Inconsistency>(corruption));
     return;
   }
 
   if (samples->TotalCount() > 0)
     histogram_flattener_->RecordDelta(*histogram, *samples);
 }
 
 void HistogramSnapshotManager::InspectLoggedSamplesInconsistency(

[Alexei Svitkine (slow), 2017/04/24 16:33:09]

I don't see this being called anywhere. Can you remove this at the same time
while you're touching this file?

[bcwhite, 2017/04/24 19:28:28]

Done.

       const HistogramSamples& new_snapshot,
       HistogramSamples* logged_samples) {
   HistogramBase::Count discrepancy =
       logged_samples->TotalCount() - logged_samples->redundant_count();
   if (!discrepancy)
     return;
 
   histogram_flattener_->InconsistencyDetectedInLoggedCount(discrepancy);
   if (discrepancy > Histogram::kCommonRaceBasedCountMismatch) {
     // Fix logged_samples.
     logged_samples->Subtract(*logged_samples);
     logged_samples->Add(new_snapshot);
   }
 }
 
 }  // namespace base