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..0717cc8079b32b7828a7d968429c2d7cd4e9856d 100644
--- a/chrome/browser/system_monitor/media_device_notifications_chromeos.cc
+++ b/chrome/browser/system_monitor/media_device_notifications_chromeos.cc
@@ -46,9 +46,15 @@ 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);
 }
 
 MediaDeviceNotifications::~MediaDeviceNotifications() {
+  if (base::SystemMonitor::Get() &&
+      base::SystemMonitor::Get()->storage_free_space_delegate())
+    base::SystemMonitor::Get()->set_storage_free_space_delegate(NULL);
+
   disks::DiskMountManager* manager = disks::DiskMountManager::GetInstance();
   if (manager) {
     manager->RemoveObserver(this);
@@ -160,4 +166,12 @@ void MediaDeviceNotifications::AddMountedPathOnUIThread(
       mount_info.mount_path);
 }
 
+void MediaDeviceNotifications::StartWatchingStorage(const FilePath& path) {
+  NOTIMPLEMENTED();
+}
+
+void MediaDeviceNotifications::StopWatchingStorage(const FilePath& path) {
+  NOTIMPLEMENTED();
+}
+
 }  // namespace chrome