Record swap metrics

content/browser/memory/swap_metrics_observer_linux.h

+// Copyright 2017 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 CONTENT_BROWSER_MEMORY_SWAP_METRICS_OBSERVER_LINUX_H_
+#define CONTENT_BROWSER_MEMORY_SWAP_METRICS_OBSERVER_LINUX_H_
+
+#include "content/browser/memory/swap_metrics_observer.h"
+
+namespace content {
+
+class SwapMetricsObserverLinux : public SwapMetricsObserver {
+ public:
+  static SwapMetricsObserverLinux* GetInstance();

[Primiano Tucci (use gerrit), 2017/04/27 10:01:20]

you don't seem to make any use of this specialized GetInstance, other than using
that in the general GetInstance that returns just a SMO. Can you just use and
return the singleton directly in the SwapMetricsObserver*
SwapMetricsObserver::GetInstance()
implementation?

[bashi, 2017/04/28 02:05:35]

Done.

+
+  SwapMetricsObserverLinux();
+  ~SwapMetricsObserverLinux() override;
+
+ protected:
+  void UpdateMetricsInternal(base::TimeDelta interval) override;
+
+ private:
+  friend struct base::LeakySingletonTraits<SwapMetricsObserverLinux>;
+
+  uint64_t last_pswpin_ = 0;
+  uint64_t last_pswpout_ = 0;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEMORY_SWAP_METRICS_OBSERVER_LINUX_H_