In the Date constructor or Date.parse, other browsers will accept time
zones like GMT-8, but before this patch, Chrome would interpret 8 as
8 minutes. This patch interprets GMT-+ a one or two digit number as hours,
not minutes.

R=adamk,jshin@chromium.org
LOG=Y
BUG=chromium:422858

Review URL: https://codereview.chromium.org/1557053002

Cr-Commit-Position: refs/heads/master@{#33100}