add: usedWidth += button.boxObject.width; 
context:   resizeFunc: function(event)   {     if (event && event.type == 'focus')       window.removeEventListener('focus', BookmarksToolbar.resizeFunc, false); // hack for bug 266737    var buttons = document.getElementById("bookmarks-ptf");    if (!buttons)      return;    var chevron = document.getElementById("bookmarks-chevron");    var width = window.innerWidth;    if (width == 0) {  // hack for bug 266737      window.addEventListener('focus', BookmarksToolbar.resizeFunc, false);      return;    }    var myToolbar = buttons.parentNode.parentNode.parentNode;    for (var i = myToolbar.childNodes.length-1; i >= 0; i--){      var anItem = myToolbar.childNodes[i];      if (anItem.id == "personal-bookmarks") {        break;      }      width -= anItem.boxObject.width;    }    var chevronWidth = 0;    chevron.collapsed = false;    chevronWidth = chevron.boxObject.width;    chevron.collapsed = true;    var overflowed = false;    var isLTR=window.getComputedStyle(document.getElementById("PersonalToolbar"),'').direction=='ltr';    for (var i=0; i<buttons.childNodes.length; i++) {      var button = buttons.childNodes[i];      button.collapsed = overflowed;            if (i == buttons.childNodes.length - 1) // last ptf item...        chevronWidth = 0;      var offset = isLTR ? button.boxObject.x                          : width - button.boxObject.x;      if (offset + button.boxObject.width + chevronWidth > width) {         overflowed = true;        // This button doesn't fit. Show it in the menu. Hide it in the toolbar.        if (!button.collapsed)          button.collapsed = true;        if (chevron.collapsed) {          chevron.collapsed = false;          var overflowPadder = document.getElementById("overflow-padder");          offset = isLTR ? buttons.boxObject.x                          : width - buttons.boxObject.x - buttons.boxObject.width;          overflowPadder.width = width - chevron.boxObject.width - offset;        }      }    }    BookmarksToolbarRDFObserver._overflowTimerInEffect = false;  },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/5b937cede80465a9a38394bb444f5d175e41066c/bookmarksMenu.js/clean/browser/components/bookmarks/content/bookmarksMenu.js