Add comments describing some more files.

git-svn-id: svn://10.0.0.236/trunk@193306 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/content/base/src/nsScriptEventManager.cpp

@@ -36,6 +36,12 @@
  *
  * ***** END LICENSE BLOCK ***** */
 
+/*
+ * Class that allows finding an event handler <script> node (one using
+ * FOR="....") for a given event and dispatching the event to that
+ * node.
+ */
+
 #include "nsScriptEventManager.h"
 
 #include "nsString.h"