GitLab

Add a "timezonechange" event and add ontimezonechange event handler
to WindowEventHandlers and WorkerGlobalScope interface.

Design Doc https://docs.google.com/document/d/1gu-HAVIjVxfPQEE0uQg9Y4tJwYl33Y54DKTA9hfDyic/edit#
I2I: https://groups.google.com/a/chromium.org/forum/#!searchin/blink-dev/timezonechange%7Csort:date/blink-dev/4BUSE2aTQEc/bahW7wniCAAJ
Behind the blink feature flag TimeZoneChangeEvent

Bug: 908550
Change-Id: I582d43ac2c1335cb5443979b3f1019a715dc35fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1994529
Commit-Queue: Frank Tang <ftang@chromium.org>
Reviewed-by: Mason Freed <masonfreed@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737841}