components/metrics: Add runtime memory leak detector

third_party/tcmalloc/chromium/src/base/custom_allocator.h

+// Copyright (c) 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.
+
+// ---
+// Author: Simon Que
+
+#ifndef BASE_CUSTOM_ALLOCATOR_H_
+#define BASE_CUSTOM_ALLOCATOR_H_
+
+#include <stddef.h>
+
+#include "base/low_level_alloc.h"
+
+// A container class for using LowLevelAlloc with STL_Allocator. The functions
+// Allocate() and Free() must match the specificiations in STL_Allocator.
+class CustomAllocator {
+ public:
+  // If no arena is provided, LowLevelAlloc still uses its default arena.
+  static void SetArena(LowLevelAlloc::Arena* arena);
+
+  static void* Allocate(size_t size);
+  static void Free(void* ptr, size_t size);
+
+ private:
+  static LowLevelAlloc::Arena* arena_;
+};
+
+#endif  // BASE_CUSTOM_ALLOCATOR_H_