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Part 3 of the work to allow wpt to set timezone during the test.
This allow ChromeDriver to set the default host timezone in the test.

* Design Doc: https://docs.google.com/document/d/1QAMHl7qIfGyFmWxta8OpR2YwivwaVgX_ixG17QWAgd0/edit#
* API Spec of the SetTimezone WebDriver Extension:
https://docs.google.com/document/d/12vdPTH_Vlkt4pxwlWzR1CjKtLE6y2Z-Qs-GPi_hWXqc/edit#
* Design Doc of the "Chromium DevTools design doc: timezone emulation"
https://docs.google.com/document/d/1ZH2jw1uFWX5uKwiIwv9mgpyBBAdwv95nb8gIRuX4W3k/edit#heading=h.7nki9mck5t64



Bug: 1144403
Change-Id: Iae396a68fb79152a684f95a989c430f4e91c86f8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2512788Reviewed-by: Shengfa Lin <shengfa@google.com>
Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Shengfa Lin <shengfa@google.com>
Cr-Commit-Position: refs/heads/master@{#823790}