I'd like to take over this bug.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e5bc23a49aa3a09d6c9b0eba268475626e64b4dc

commit e5bc23a49aa3a09d6c9b0eba268475626e64b4dc
Author: Gyuyoung Kim <gyuyoung@igalia.com>
Date: Wed Jan 16 02:05:04 2019

s13n: Remove oauth2_token_service.h include from gcd_api_flow.h

There is no use of OAuth2TokenService in GCDApiFlow. So we don't need
to keep the oauth2_token_service.h include in gcd_api_flow.h.

Bug:  921606 
Change-Id: Ie5b18bb96a4994453cd826349abdf24b99f3b16f
Reviewed-on: https://chromium-review.googlesource.com/c/1411095
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/master@{#623026}
[modify] https://crrev.com/e5bc23a49aa3a09d6c9b0eba268475626e64b4dc/chrome/browser/printing/cloud_print/gcd_api_flow.h