Disable test_punycodeURIs.js on mac only, part of bug 450884.

mail/app/Makefile.in

@@ -405,3 +405,11 @@ libs::
 	if test -f $(DIST)/../_tests/xpcshell-simple/test_necko/unit/test_cookie_header.js; then echo "function run_test() {dump('disabled for TB for bug 431125');}" >$(DIST)/../_tests/xpcshell-simple/test_necko/unit/test_cookie_header.js; fi;
 	$(RM) $(DIST)/bin/TestCookie
 	if test -f $(DIST)/bin/TestTArray; then cp $(DIST)/bin/TestTArray $(DIST)/bin/TestCookie; fi;
+
+ifneq (,$(filter mac cocoa,$(MOZ_WIDGET_TOOLKIT)))
+
+# Disabled due to bug 447999
+libs::
+	if test -f $(DIST)/../_tests/xpcshell-simple/test_uriloader_exthandler/unit/test_punycodeURIs.js; then echo "function run_test() {dump('disabled for bug 447999');}" >$(DIST)/../_tests/xpcshell-simple/test_uriloader_exthandler/unit/test_punycodeURIs.js; fi;
+
+endif