De-duplicate ranges information in persistent memory.

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 413 matching lines @@
 // static
 size_t StatisticsRecorder::GetHistogramCount() {
   base::AutoLock auto_lock(lock_.Get());
   if (!histograms_)
     return 0;
   return histograms_->size();
 }
 
 // static
 void StatisticsRecorder::ForgetHistogramForTesting(base::StringPiece name) {
-  if (histograms_)
-    histograms_->erase(name);
+  if (!histograms_)
+    return;
+
+  HistogramMap::iterator found = histograms_->find(name);
+  if (found == histograms_->end())
+    return;
+
+  HistogramBase* base = found->second;
+  if (base->GetHistogramType() != SPARSE_HISTOGRAM) {

[Alexei Svitkine (slow), 2017/04/04 17:45:09]

Nit: Add a comment about this logic.

[bcwhite, 2017/04/05 13:41:30]

Done.

+    Histogram* histogram = static_cast<Histogram*>(base);
+    histogram->bucket_ranges()->set_persistent_reference(0);
+  }
+
+  histograms_->erase(found);
 }
 
 // static
 std::unique_ptr<StatisticsRecorder>
 StatisticsRecorder::CreateTemporaryForTesting() {
   return WrapUnique(new StatisticsRecorder());
 }
 
 // static
 void StatisticsRecorder::UninitializeForTesting() {
@@ skipping 87 matching lines @@
 StatisticsRecorder::CallbackMap* StatisticsRecorder::callbacks_ = nullptr;
 // static
 StatisticsRecorder::RangesMap* StatisticsRecorder::ranges_ = nullptr;
 // static
 StatisticsRecorder::HistogramProviders* StatisticsRecorder::providers_;
 // static
 base::LazyInstance<base::Lock>::Leaky StatisticsRecorder::lock_ =
     LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace base