GitLab

Relanding https://chromium-review.googlesource.com/c/chromium/src/+/1026290
with fix for build breakage (missing include file was not caught by
local build or any default trybot because it was behind a DEFINE) and
one other minor suggestion by leiz (use base::MakeRefCounted for
head.headers).

Bug: 773295
Change-Id: I25d9327a893debf35ccbc7d4f64b84b6d6e84267
Reviewed-on: https://chromium-review.googlesource.com/1031316Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Mark Pilgrim <pilgrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554393}