Add a simple network::mojom::CookieManager implementation to services/network/test

[1], [2] and [3] all have "fake" implementations of network::mojom::CookieManager,
mostly stubbed out.

This CL provides a simple implementation of this interface located in
//services/network/test/test_cookie_manager.cc|h that can be either used
as is (eg by [1] and [2]) or have the relevant methods overridden (eg in [3]).

[1] //services/identity/public/cpp/identity_manager_unittests.cc,
[2] //components/signin/core/browser/test_signin_client.cc
[3] //c/b/chromeos/android_sms/android_sms_app_setup_controller_impl_unittest.cc

For consistency, the newly added class is named TestCookieManager.

This is a follow up of [4].

[4] https://crrev.com/c/1452816/1/services/identity/public/cpp/identity_manager_unittest.cc#96

BUG=926890

Change-Id: Ie1b7b7e3dd6e432f61b91b310614645409294d89
Reviewed-on: https://chromium-review.googlesource.com/c/1456916
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630093}
6 files changed