[tests] Fix timezone dependence in an intl test

In certain timezones, being at noon UTC doesn't guarantee that
you'll be the same day in local time. This patch fixes that
false assumption. Thanks to Holmes He for reporting the issue.

Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng
Change-Id: I7432c0eb1e13fdf11c665e59dabaebeb79bff8c8
Reviewed-on: https://chromium-review.googlesource.com/568021Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Daniel Ehrenberg <littledan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46584}

test/intl/date-format/format-test.js

@@ -47,4 +47,4 @@ invalidValues.forEach(function(value) {
 
 // https://code.google.com/p/chromium/issues/detail?id=537382
 
-assertEquals('11/11/1500', dtf.format(new Date(1500,10,11,12,0,0)));
+assertEquals('11/11/1500', dtf.format(new Date(Date.UTC(1500,10,11,12,0,0))));