Make arc_robot_auth_code_fetcher_browsertest use GetSafeWeakWrapper

When using GetSafeWeakWrapper, Detach() is called automatically, so
tests don't need to call it themselves.

Bug: 924960
Change-Id: I0cf1fb8fe00a1234cc00c66d09cf1be4cecc3646
Reviewed-on: https://chromium-review.googlesource.com/c/1470690
Reviewed-by: Yury Khmel <khmel@chromium.org>
Commit-Queue: Lowell Manners <lowell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632146}
1 file changed