SyncAuthManager: Remove workarounds for ChromeOS tests

On ChromeOS, browser tests are signed in by default, but the test
account setup is a bit broken (it happens much later than in real
life). This meant that we needed some special workaround code,
essentially unnecessarily re-querying the account, just to make some
tests happy on ChromeOS.
However, the only affected tests were two sync-internals tests. This
CL just removes those ChromeOS-specific tests, which lets us also
remove all the workarounds in real code.

Bug: 814787
Change-Id: I29e5b22ebe79845cb473bc320c04f511d78e9d8d
Reviewed-on: https://chromium-review.googlesource.com/c/1206491
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#633208}
3 files changed