add: if(markRead == null) { markRead= !SelectedMessagesAreRead(); } 
context: function MsgMarkMsgAsRead(markRead){	var selectedMessages = GetSelectedMessages();	var compositeDataSource = GetCompositeDataSource("MarkMessageRead");	MarkMessagesRead(compositeDataSource, selectedMessages, markRead);}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/d63000ffb06f1c74b5d3215477135715d57355d7/mailWindowOverlay.js/clean/mailnews/base/resources/content/mailWindowOverlay.js