Eliminate IdentityManagerFactory::BuildAuthenticatedInstanceForTesting()

There are multiple layers of infrastructure to support building
IdentityManager within the ProfileKeyedService infrastructure with a
primary account from creation. This infrastructure is needed for only
one unittest, of SigninProfileAttributesUpdater.

It turns out that this unittest can easily be updated to explicitly
construct the dependencies of SigninProfileAttributesUpdater rather
than using the ProfileKeyedService infrastructure. This both makes the
test itself simpler and enables ripping out all of the aforementioned
layers of infrastructure.

Bug: 939828
Change-Id: Ibc2c8cb6e5668d9f12917b0b081ba5f9471b55df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1511973
Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639435}
7 files changed