Extend the capability of SystemMonitor to support watching storage free space change

chrome/browser/system_monitor/media_device_notifications_window_win.h

 // 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.
 
 #ifndef CHROME_BROWSER_SYSTEM_MONITOR_MEDIA_DEVICE_NOTIFICATIONS_WINDOW_WIN_H_
 #define CHROME_BROWSER_SYSTEM_MONITOR_MEDIA_DEVICE_NOTIFICATIONS_WINDOW_WIN_H_
 
 #include <windows.h>
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/memory/ref_counted.h"
 
 typedef LRESULT (*VolumeNameFunc)(LPCWSTR drive,
                                   LPWSTR volume_name,
                                   unsigned int volume_name_len);
 namespace chrome {
 
 class MediaDeviceNotificationsWindowWin
-    : public base::RefCountedThreadSafe<MediaDeviceNotificationsWindowWin> {
+    : public base::RefCountedThreadSafe<MediaDeviceNotificationsWindowWin>,
+      public base::SystemMonitor::StorageFreeSpaceDelegate {
  public:
   MediaDeviceNotificationsWindowWin();
   // Only for use in unit tests.
   explicit MediaDeviceNotificationsWindowWin(VolumeNameFunc volumeNameFunc);
 
   LRESULT OnDeviceChange(UINT event_type, DWORD data);
 
  private:
   friend class base::RefCountedThreadSafe<MediaDeviceNotificationsWindowWin>;
 
@@ skipping 13 matching lines @@
 
   void CheckDeviceTypeOnFileThread(const std::string& id,
                                    const FilePath::StringType& device_name,
                                    const FilePath& path);
 
   void ProcessMediaDeviceAttachedOnUIThread(
       const std::string& id,
       const FilePath::StringType& device_name,
       const FilePath& path);
 
+  // Overriden from SystemMonitor::StorageFreeSpaceDelegate.
+  virtual bool StartWatchingStorage(const FilePath::StringType& path) OVERRIDE;
+  virtual bool StopWatchingStorage(const FilePath::StringType& path) OVERRIDE;
+
   // The window class of |window_|.
   ATOM atom_;
 
   // The handle of the module that contains the window procedure of |window_|.
   HMODULE instance_;
 
   HWND window_;
   VolumeNameFunc volume_name_func_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaDeviceNotificationsWindowWin);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_SYSTEM_MONITOR_MEDIA_DEVICE_NOTIFICATIONS_WINDOW_WIN_H_