Record swap metrics

content/browser/memory/swap_metrics_observer_mac.cc

Index: content/browser/memory/swap_metrics_observer_mac.cc
diff --git a/content/browser/memory/swap_metrics_observer_mac.cc b/content/browser/memory/swap_metrics_observer_mac.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d44b50fe543b11a7d633a3ed138595239157e837
--- /dev/null
+++ b/content/browser/memory/swap_metrics_observer_mac.cc
@@ -0,0 +1,15 @@
+// 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"
+
+namespace content {
+
+// static
+SwapMetricsObserver* SwapMetricsObserver::GetInstance() {
+  // TODO(bashi): Implement SwapMetricsObserver for macOS.
+  return nullptr;
+}
+
+}  // namespace content