Add notification for media changed, and notify volume mount watcher when it occurs.

components/storage_monitor/volume_mount_watcher_win.h

Index: components/storage_monitor/volume_mount_watcher_win.h
diff --git a/components/storage_monitor/volume_mount_watcher_win.h b/components/storage_monitor/volume_mount_watcher_win.h
index 0940d5c01117de4c0c698d39d15f43c643644146..5e5f05a5e94ce14ed8f6f06658bb6487d635d768 100644
--- a/components/storage_monitor/volume_mount_watcher_win.h
+++ b/components/storage_monitor/volume_mount_watcher_win.h
@@ -49,6 +49,9 @@ class VolumeMountWatcherWin {
   // notification if appropriate.
   void OnWindowMessage(UINT event_type, LPARAM data);
 
+  // Processes SHCNE_MEDIAINSERTED (and REMOVED).
+  void OnMediaChange(WPARAM wparam, LPARAM lparam);
+
   // Set the volume notifications object to be used when new
   // removable volumes are found.
   void SetNotifications(StorageMonitor::Receiver* notifications);