Record swap metrics

content/browser/memory/swap_metrics_observer.cc

+// 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.
+
+#include "content/browser/memory/swap_metrics_observer.h"
+
+#include "base/bind.h"
+#include "base/threading/thread_task_runner_handle.h"
+
+namespace content {
+
+namespace {
+
+// Time between updating swap rates.
+const int kSwapMetricsIntervalSeconds = 60;
+}

[Ilya Sherman, 2017/04/28 21:10:20]

nit: Please leave a blank line before this closing brace, and add "  //
namespace" to the end of this line.

[bashi, 2017/05/01 01:14:13]

Done.

+
+SwapMetricsObserver::SwapMetricsObserver()
+    : update_interval_(
+          base::TimeDelta::FromSeconds(kSwapMetricsIntervalSeconds)) {}
+
+SwapMetricsObserver::~SwapMetricsObserver() {}
+
+void SwapMetricsObserver::Start() {
+  timer_.Start(FROM_HERE, update_interval_, this,
+               &SwapMetricsObserver::UpdateMetrics);
+}
+
+void SwapMetricsObserver::Stop() {
+  last_ticks_ = base::TimeTicks();
+  timer_.Stop();
+}
+
+void SwapMetricsObserver::UpdateMetrics() {
+  base::TimeTicks now = base::TimeTicks::Now();
+  base::TimeDelta interval =
+      last_ticks_.is_null() ? base::TimeDelta() : now - last_ticks_;
+  UpdateMetricsInternal(interval);
+  last_ticks_ = now;
+}
+
+}  // namespace content