Bug 1533584 - Enable capping the maximum life-time of client-side cookies to seven days on Nightly; r=baku

Differential Revision: https://phabricator.services.mozilla.com/D24098

--HG--
extra : moz-landing-system : lando

modules/libpref/init/StaticPrefList.h

@@ -2171,11 +2171,17 @@ VARCACHE_PREF(
 )
 
 // Maximum client-side cookie life-time cap
+#ifdef NIGHTLY_BUILD
+# define PREF_VALUE 604800 // 7 days
+#else
+# define PREF_VALUE 0
+#endif
 VARCACHE_PREF(
   "privacy.documentCookies.maxage",
    privacy_documentCookies_maxage,
-  uint32_t, 0 // Disabled (in seconds, set to 0 to disable)
+  uint32_t, PREF_VALUE // (in seconds, set to 0 to disable)
 )
+#undef PREF_VALUE
 
 // Anti-fingerprinting, disabled by default
 VARCACHE_PREF(