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

chrome/browser/system_monitor/media_device_notifications_chromeos.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.
 
 // chromeos::MediaDeviceNotifications listens for mount point changes and
 // notifies the SystemMonitor about the addition and deletion of media devices.
 
 #ifndef CHROME_BROWSER_SYSTEM_MONITOR_MEDIA_DEVICE_NOTIFICATIONS_CHROMEOS_H_
 #define CHROME_BROWSER_SYSTEM_MONITOR_MEDIA_DEVICE_NOTIFICATIONS_CHROMEOS_H_
 
 #if !defined(OS_CHROMEOS)
 #error "Should only be used on ChromeOS."
 #endif
 
 #include <map>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/system_monitor/system_monitor.h"
 #include "chromeos/disks/disk_mount_manager.h"
 
 namespace chromeos {
 
 class MediaDeviceNotifications
     : public base::RefCountedThreadSafe<MediaDeviceNotifications>,
-      public disks::DiskMountManager::Observer {
+      public disks::DiskMountManager::Observer,
+      public base::SystemMonitor::StorageFreeSpaceDelegate {
  public:
   MediaDeviceNotifications();
 
   virtual void DiskChanged(disks::DiskMountManagerEventType event,
                            const disks::DiskMountManager::Disk* disk) OVERRIDE;
   virtual void DeviceChanged(disks::DiskMountManagerEventType event,
                              const std::string& device_path) OVERRIDE;
   virtual void MountCompleted(
       disks::DiskMountManager::MountEvent event_type,
       MountError error_code,
@@ skipping 15 matching lines @@
   // Checks if the mount point in |mount_info| is a media device. If it is,
   // then continue with AddMountedPathOnUIThread() below.
   void CheckMountedPathOnFileThread(
       const disks::DiskMountManager::MountPointInfo& mount_info);
 
   // Adds the mount point in |mount_info| to |mount_map_| and send a media
   // device attach notification.
   void AddMountedPathOnUIThread(
       const disks::DiskMountManager::MountPointInfo& mount_info);
 
+  // Overriden from SystemMonitor::StorageFreeSpaceDelegate.
+  virtual bool StartWatchingStorage(const FilePath::StringType& path) OVERRIDE;
+  virtual bool StopWatchingStorage(const FilePath::StringType& path) OVERRIDE;
+
   // Mapping of relevant mount points and their corresponding mount devices.
   // Only accessed on the UI thread.
   MountMap mount_map_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaDeviceNotifications);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_SYSTEM_MONITOR_MEDIA_DEVICE_NOTIFICATIONS_CHROMEOS_H_