[Tentaive patch for discussion] Add Purge+Suspend metrics as UMA.

base/memory/malloc_statistics.h

+// Copyright 2016 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_MEMORY_MALLOC_STATISTICS_H_
+#define BASE_MEMORY_MALLOC_STATISTICS_H_
+
+#include <stddef.h>
+
+#include "base/base_export.h"
+
+namespace base {
+namespace memory {
+
+struct BASE_EXPORT MallocStatistics {
+  size_t allocated_objects_size;
+  size_t allocated_objects_count;
+  size_t metadata_fragmentation_caches;
+  size_t total_virtual_size;
+  size_t resident_size;
+
+  MallocStatistics()
+      : allocated_objects_size(0),
+        allocated_objects_count(0),
+        metadata_fragmentation_caches(0),
+        total_virtual_size(0),
+        resident_size(0) {}
+
+  static MallocStatistics GetStatistics();
+};
+
+}  // namespace trace_event
+}  // namespace base
+
+#endif  // BASE_MEMORY_MALLOC_STATISTICS_H_