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

chrome/browser/system_monitor/removable_device_notifications_chromeos.h

Index: chrome/browser/system_monitor/removable_device_notifications_chromeos.h
diff --git a/chrome/browser/system_monitor/removable_device_notifications_chromeos.h b/chrome/browser/system_monitor/removable_device_notifications_chromeos.h
index cae24604fbe21324fcc1740f9f51a85229d17ef2..30c320a4efcd7530a5b2b40f1ddfc464889476c3 100644
--- a/chrome/browser/system_monitor/removable_device_notifications_chromeos.h
+++ b/chrome/browser/system_monitor/removable_device_notifications_chromeos.h
@@ -27,6 +27,7 @@ namespace chromeos {
 class RemovableDeviceNotificationsCros
     : public base::RefCountedThreadSafe<RemovableDeviceNotificationsCros>,
       public disks::DiskMountManager::Observer {
+      public base::SystemMonitor::StorageFreeSpaceDelegate {
  public:
   RemovableDeviceNotificationsCros();
 
@@ -64,6 +65,10 @@ class RemovableDeviceNotificationsCros
       const disks::DiskMountManager::MountPointInfo& mount_info,
       bool has_dcim);
 
+  // Overriden from SystemMonitor::StorageFreeSpaceDelegate.
+  virtual void StartWatchingStorage(const FilePath& path) OVERRIDE;
+  virtual void StopWatchingStorage(const FilePath& path) OVERRIDE;
+
   // Mapping of relevant mount points and their corresponding mount devices.
   // Only accessed on the UI thread.
   MountMap mount_map_;