add: if(markRead == null) { markRead= !SelectedMessagesAreRead(); } 
context: function MsgMarkMsgAsRead(markRead){	var selectedMessages = GetSelectedMessages();	var compositeDataSource = GetCompositeDataSource("MarkMessageRead");	MarkMessagesRead(compositeDataSource, selectedMessages, markRead);}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/0938bbb70031b70863a26099bd6eab59d9a14e34/mailWindowOverlay.js/clean/mailnews/base/resources/content/mailWindowOverlay.js