Udev-related methods are extracted from HidServiceLinux into individual service.

device/hid/device_monitor_linux.h

Index: device/hid/device_monitor_linux.h
diff --git a/device/hid/device_monitor_linux.h b/device/hid/device_monitor_linux.h
new file mode 100644
index 0000000000000000000000000000000000000000..d198473186ac0567bbf8a4d2afb9b9c4fe2a589b
--- /dev/null
+++ b/device/hid/device_monitor_linux.h
@@ -0,0 +1,60 @@
+// 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.
+
+#ifndef DEVICE_HID_DEVICE_MONITOR_LINUX_H_
+#define DEVICE_HID_DEVICE_MONITOR_LINUX_H_
+
+#include <string>
+
+#include "base/compiler_specific.h"
+#include "base/macros.h"
+#include "base/message_loop/message_pump_libevent.h"
+#include "base/observer_list.h"
+#include "device/hid/udev_common.h"
+
+struct udev_device;
+
+namespace device {
+
+class DeviceMonitorLinux : public base::MessagePumpLibevent::Watcher {
+ public:
+  typedef base::Callback<void(udev_device* device)> EnumerateCallback;
+
+  class Observer {
+   public:
+    virtual ~Observer() {}
+    virtual void OnDeviceAdded(udev_device* device) = 0;
+    virtual void OnDeviceRemoved(udev_device* device) = 0;
+  };
+
+  DeviceMonitorLinux();
+  virtual ~DeviceMonitorLinux();
+
+  static DeviceMonitorLinux* GetInstance();
+  static bool HasInstance();
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+  ScopedUdevDevicePtr GetDeviceFromPath(const std::string& path);
+  void Enumerate(const EnumerateCallback& callback);
+
+  // Implements base::MessagePumpLibevent::Watcher
+  virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
+  virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
+
+ private:
+  ScopedUdevPtr udev_;
+  ScopedUdevMonitorPtr monitor_;
+  int monitor_fd_;
+  base::MessagePumpLibevent::FileDescriptorWatcher monitor_watcher_;
+
+  ObserverList<Observer> observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(DeviceMonitorLinux);
+};
+
+}  // namespace device
+
+#endif  // DEVICE_HID_DEVICE_MONITOR_LINUX_H_