Ship CSS gradient color stop double-position syntax

Intent-to-Ship thread:

 https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/8B9FbeTBIK0/DNkC2pz-AAAJ

Also removing the actual feature and corresponding check, because it's
only used in a single spot, so if the feature should need to be
unshipped it ought to be a fairly trivial revert.

Bug: 707047, 880733
Change-Id: Ie854d7fd9f7a22e9c6144668a37f694dd1c508ee
Reviewed-on: https://chromium-review.googlesource.com/1230018
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#592028}
2 files changed