Add DeviceMonitorLinux in BrowserMainLoop.

content/browser/devices_monitor/devices_monitor_mac.mm

+// Copyright (c) 2012 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/devices_monitor/devices_monitor_mac.h"
+
+namespace content {
+
+// static
+DevicesMonitor* DevicesMonitor::Create() {
+  return new DevicesMonitorMac();
+}
+
+DevicesMonitorMac::DevicesMonitorMac() {}
+
+DevicesMonitorMac::~DevicesMonitorMac() {}
+
+void DevicesMonitorMac::Start(
+    base::SystemMonitor::DevicesChangedObserver* observer) {
+}
+
+void DevicesMonitorMac::Stop(
+    base::SystemMonitor::DevicesChangedObserver* observer) {
+}
+
+}  // namespace content