GitLab

This CL only migrates DiceResponseHandler production code away from
SigninManager, leaves migration away from ProfileOAuth2TokenService
and unittests for a follow up step.

Note that the unittest c/b/signin/dice_response_handler_unittest.cc
was minimally updated to keep passing.

BUG=890790,902296

Change-Id: Iecdf43b80afe6514b7f19075c2bb62aadfbdbe4c
Reviewed-on: https://chromium-review.googlesource.com/c/1318550
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606439}