On chrome://sync-internals, also show the time when an auth error was set

In some past investigations, it might have been useful to know since
when an auth error state has existed.

Bug: 948074
Change-Id: I4220dbea552725cd0d75b35e563e292f7d5eea12
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1557027
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649054}
11 files changed