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

chrome/browser/system_monitor/media_device_notifications_chromeos.cc

Index: chrome/browser/system_monitor/media_device_notifications_chromeos.cc
diff --git a/chrome/browser/system_monitor/media_device_notifications_chromeos.cc b/chrome/browser/system_monitor/media_device_notifications_chromeos.cc
index 9855874169a07623bd5fbcf21c3a3ad59674132c..505b3820cdfc78edc3f552a59100df38059f38be 100644
--- a/chrome/browser/system_monitor/media_device_notifications_chromeos.cc
+++ b/chrome/browser/system_monitor/media_device_notifications_chromeos.cc
@@ -46,9 +46,13 @@ MediaDeviceNotifications::MediaDeviceNotifications() {
   DCHECK(disks::DiskMountManager::GetInstance());
   disks::DiskMountManager::GetInstance()->AddObserver(this);
   CheckExistingMountPointsOnUIThread();
+  if (base::SystemMonitor::Get())
+    base::SystemMonitor::Get()->set_storage_free_space_delegate(this);

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

Since free space observer isn't really implemented in these classes yet.  Add a
comment to the delegate set code that it needs to be called on the thread that
will be starting and stopping observation.

[Hongbo Min, 2012/09/13 13:40:53]

Done.

 }
 
 MediaDeviceNotifications::~MediaDeviceNotifications() {
+  if (base::SystemMonitor::Get())

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

Since we're removing the delegate here, we'll need to check that the delegate
isn't null before each use in SystemMonitor.

[Hongbo Min, 2012/09/13 13:40:53]

Done.

+    base::SystemMonitor::Get()->set_storage_free_space_delegate(NULL);
   disks::DiskMountManager* manager = disks::DiskMountManager::GetInstance();
   if (manager) {
     manager->RemoveObserver(this);
@@ -160,4 +164,17 @@ void MediaDeviceNotifications::AddMountedPathOnUIThread(
       mount_info.mount_path);
 }
 
+bool MediaDeviceNotifications::IsWatchingStorage(const FilePath& path) {
+  NOTIMPLEMENTED();
+  return false;
+}
+
+void MediaDeviceNotifications::StartWatchingStorage(const FilePath& path) {
+  NOTIMPLEMENTED();
+}
+
+void MediaDeviceNotifications::StopWatchingStorage(const FilePath& path) {
+  NOTIMPLEMENTED();
+}
+
 }  // namespace chrome