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

chrome/browser/system_monitor/removable_device_notifications_mac.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_REMOVABLE_DEVICE_NOTIFICATIONS_MAC_H_
 #define CHROME_BROWSER_SYSTEM_MONITOR_REMOVABLE_DEVICE_NOTIFICATIONS_MAC_H_
 
 #include <DiskArbitration/DiskArbitration.h>
 #include <map>
 
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/weak_ptr.h"
 #include "base/system_monitor/system_monitor.h"
 #include "chrome/browser/system_monitor/disk_info_mac.h"
 
 namespace chrome {
 
 // This class posts notifications to base::SystemMonitor when a new disk
 // is attached, removed, or changed.
 class RemovableDeviceNotificationsMac :
-    public base::SupportsWeakPtr<RemovableDeviceNotificationsMac> {
+    public base::SupportsWeakPtr<RemovableDeviceNotificationsMac>,
+    public base::SystemMonitor::StorageFreeSpaceDelegate {
  public:
   enum UpdateType {
     UPDATE_DEVICE_ADDED,
     UPDATE_DEVICE_CHANGED,
     UPDATE_DEVICE_REMOVED,
   };
 
   RemovableDeviceNotificationsMac();
   virtual ~RemovableDeviceNotificationsMac();
 
   void UpdateDisk(const DiskInfoMac& info, UpdateType update_type);
 
   bool GetDeviceInfoForPath(
       const FilePath& path,
       base::SystemMonitor::RemovableStorageInfo* device_info) const;
 
+  // Overriden from SystemMonitor::StorageFreeSpaceDelegate.
+  virtual void StartWatchingStorage(const FilePath& path) OVERRIDE;
+  virtual void StopWatchingStorage(const FilePath& path) OVERRIDE;
+
  private:
   static void DiskAppearedCallback(DADiskRef disk, void* context);
   static void DiskDisappearedCallback(DADiskRef disk, void* context);
   static void DiskDescriptionChangedCallback(DADiskRef disk,
                                              CFArrayRef keys,
                                              void *context);
 
   bool ShouldPostNotificationForDisk(const DiskInfoMac& info) const;
   bool FindDiskWithMountPoint(const FilePath& mount_point,
                               DiskInfoMac* info) const;
 
   base::mac::ScopedCFTypeRef<DASessionRef> session_;
   // Maps disk bsd names to disk info objects. This map tracks all mountable
   // devices on the system though only notifications for removable devices are
   // posted.
   std::map<std::string, DiskInfoMac> disk_info_map_;
 
   DISALLOW_COPY_AND_ASSIGN(RemovableDeviceNotificationsMac);
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_SYSTEM_MONITOR_REMOVABLE_DEVICE_NOTIFICATIONS_MAC_H_