GitLab

This service uses a HEAD request in order to check if the specified URL
can resolve to an existing page. This will be used in the New Tab Page
in order to check if a new custom link URL (obtained from adding or
editing) can resolve.

Split from https://crrev.com/c/1249567.

Bug: 874194
Change-Id: I46be9a09d6f07988c468e9e025bed4117df61437
Reviewed-on: https://chromium-review.googlesource.com/c/1259664
Commit-Queue: Kristi Park <kristipark@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597630}