Refactor Udev device support in Ozone and add a DRM hotplug monitor

ui/events/ozone/device/device_manager_manual.cc

+// Copyright 2014 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 "ui/events/ozone/device/device_manager_manual.h"
+
+#include "base/files/file_enumerator.h"
+#include "ui/events/ozone/device/device_event.h"
+#include "ui/events/ozone/device/device_event_observer.h"
+
+namespace ui {
+
+DeviceManagerManual::DeviceManagerManual() {}
+
+DeviceManagerManual::~DeviceManagerManual() {}
+
+void DeviceManagerManual::ScanDevices(DeviceEventObserver* observer) {
+  base::FileEnumerator file_enum(base::FilePath("/dev/input"),
+                                 false,
+                                 base::FileEnumerator::FILES,
+                                 "event*[0-9]");
+  for (base::FilePath path = file_enum.Next(); !path.empty();
+       path = file_enum.Next()) {
+    DeviceEvent event(DeviceEvent::INPUT, DeviceEvent::ADD, path);
+    observer->OnDeviceEvent(event);
+  }
+}
+
+void DeviceManagerManual::AddObserver(DeviceEventObserver* observer) {}
+
+void DeviceManagerManual::RemoveObserver(DeviceEventObserver* observer) {}
+
+}  // namespace ui