components/metrics: Add runtime memory leak detector

components/metrics/leak_detector/ranked_list.h

Index: components/metrics/leak_detector/ranked_list.h
diff --git a/components/metrics/leak_detector/ranked_list.h b/components/metrics/leak_detector/ranked_list.h
new file mode 100644
index 0000000000000000000000000000000000000000..4672d31af98cc7730e089f237f6a411d4b70f78b
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+++ b/components/metrics/leak_detector/ranked_list.h
@@ -0,0 +1,72 @@
+// Copyright 2015 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 COMPONENTS_METRICS_LEAK_DETECTOR_RANKED_LIST_H_
+#define COMPONENTS_METRICS_LEAK_DETECTOR_RANKED_LIST_H_
+
+#include <stdint.h>
+
+#include <vector>
+
+#include "components/metrics/leak_detector/leak_detector_value_type.h"
+#include "components/metrics/leak_detector/stl_allocator.h"
+#include <gperftools/custom_allocator.h>
+
+// RankedList lets you add entries and automatically sorts them internally, so
+// they can be accessed in sorted order. The entries are stored as a vector
+// array.
+
+namespace leak_detector {
+
+class RankedList {
+ public:
+  using ValueType = LeakDetectorValueType;
+
+  // A single entry in the RankedList. The RankedList sorts entries by |count|.
+  struct Entry {
+    int count;
+    ValueType value;
+  };
+
+  explicit RankedList(size_t max_size) : max_size_(max_size) {
+    entries_.reserve(max_size + 1);
+  }
+  ~RankedList() {}
+
+  // Access individual element. Does not do boundary checking.
+  const Entry& entry(int index) const {
+    return entries_[index];
+  }
+
+  size_t size() const {
+    return entries_.size();
+  }
+
+  // Add a new value-count pair to the list. Does not check for existing entries
+  // with the same value.
+  void Add(const ValueType& value, int count);
+
+ private:
+  // Returns the position to insert a new value. Returns -1 if it cannot be
+  // inserted.
+  int GetInsertionIndex(int count) const;
+
+  // Max and min counts. Returns 0 if the list is empty.
+  const int max_count() const {
+    return entries_.empty() ? 0 : entries_[0].count;
+  }
+  const int min_count() const {
+    return entries_.empty() ? 0 : entries_[size() - 1].count;
+  }
+
+  // Max number of items in the list.
+  size_t max_size_;
+
+  // Points to the array of entries.
+  std::vector<Entry, STL_Allocator<Entry, CustomAllocator>> entries_;
+};
+
+}  // namespace leak_detector
+
+#endif  // COMPONENTS_METRICS_LEAK_DETECTOR_RANKED_LIST_H_