Enable fastback (saving 3 content viewers). Bug 298293, r+sr=darin, a=bsmedberg

suite/browser/browser-prefs.js

@@ -111,6 +111,7 @@ pref("browser.search.param.Google.1.default", "chrome://navigator/content/search
 
 pref("browser.history.grouping", "day");
 pref("browser.sessionhistory.max_entries", 50);
+pref("browser.sessionhistory.max_viewers", 3);
 
 // Tabbed browser
 pref("browser.tabs.loadDivertedInBackground", false);