[NTP OptOut] Refactoring tests

A promissed follow-up test refactoring, which removes friending of test
classes. It also found a bug, already fixed in original patch.

Bug: 805171
Change-Id: I1d7c3a8043df705f3e21cd7dabdab401b424f08f
Reviewed-on: https://chromium-review.googlesource.com/903586
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Reviewed-by: Jan Krcal <jkrcal@chromium.org>
Reviewed-by: Tim Schumann <tschumann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536045}
2 files changed