Bug 920750 - Disable update xml certificate checks on Mac OS X. r=bbondy

browser/app/profile/firefox.js

@@ -102,10 +102,10 @@ pref("app.update.log", false);
 pref("app.update.backgroundMaxErrors", 10);
 
 // The aus update xml certificate checks for application update are disabled on
-// Windows since the mar signature check which is currently only implemented on
-// Windows is sufficient for preventing us from applying a mar that is not
+// Windows and Mac OS X since the mar signature check are implemented on these
+// platforms and is sufficient to prevent us from applying a mar that is not
 // valid.
-#ifdef XP_WIN
+#if defined(XP_WIN) || defined(XP_MACOSX)
 pref("app.update.cert.requireBuiltIn", false);
 pref("app.update.cert.checkAttributes", false);
 #else