>>23
19〜21行目
this.tabContext = document.getAnonymousElementByAttribute( ...略... gBrowser.tabContainer.contextMenu;
　↓
this.tabContext = document.getElementById("contentAreaContextMenu");

40行目
"tabContextHistoryMenu.populateTabContextHistoryMenu(gBrowser.mContextTab);");
　↓
"tabContextHistoryMenu.populateTabContextHistoryMenu(gBrowser.selectedTab);");

75行目
var aTab = window.gBrowser.mContextTab;
　↓
var aTab = window.gBrowser.selectedTab;