add: gPrevCharset = gLastBrowserCharset; 
context: function charsetLoadListener (event){    var charset = window._content.document.characterSet;    if (charset.length > 0 && (charset != gLastBrowserCharset)) {        gCharsetMenu.SetCurrentCharset(charset);        gLastBrowserCharset = charset;    }}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/ed5343a114456b3edb5b800bc2819e9cd263f7f3/charsetOverlay.js/clean/xpfe/global/resources/content/charsetOverlay.js