partial fix for bug #332748:

Figure out how much history we can show by default.

bump the default from 9 days to 180 days.

r=mconnor

browser/app/profile/firefox.js

@@ -234,6 +234,7 @@ pref("browser.search.suggest.enabled", true);
 pref("browser.history.grouping", "day");
 pref("browser.history.showSessions", false);
 pref("browser.sessionhistory.max_entries", 50);
+pref("browser.history_expire_days", 180);
 
 // handle external links
 // 0=default window, 1=current window/tab, 2=new window, 3=new tab in most recent window