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

chrome/browser/system_monitor/media_device_notifications_window_win.h

Index: chrome/browser/system_monitor/media_device_notifications_window_win.h
diff --git a/chrome/browser/system_monitor/media_device_notifications_window_win.h b/chrome/browser/system_monitor/media_device_notifications_window_win.h
index 26407a70c28cc92788534c011ad7cf86d54f560b..13bc2f835ddfebe91cb038aee0086fac917a4532 100644
--- a/chrome/browser/system_monitor/media_device_notifications_window_win.h
+++ b/chrome/browser/system_monitor/media_device_notifications_window_win.h
@@ -19,7 +19,8 @@ typedef LRESULT (*VolumeNameFunc)(LPCWSTR drive,
 namespace chrome {
 
 class MediaDeviceNotificationsWindowWin
-    : public base::RefCountedThreadSafe<MediaDeviceNotificationsWindowWin> {
+    : public base::RefCountedThreadSafe<MediaDeviceNotificationsWindowWin>,
+      public base::SystemMonitor::StorageFreeSpaceDelegate {
  public:
   MediaDeviceNotificationsWindowWin();
   // Only for use in unit tests.
@@ -53,6 +54,10 @@ class MediaDeviceNotificationsWindowWin
       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_;