Changed the filename logo_tracker.h to logo_observer.h

LogoTracker has been merged into LogoService.
So only LogoObserver was left in the logo_tracker.h

Bug: 761829
Change-Id: I95aa1f4391ecfd66dcb436d5df76ab4e211a4a98
Reviewed-on: https://chromium-review.googlesource.com/c/1371305
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Reviewed-by: Kyle Milka <kmilka@chromium.org>
Commit-Queue: Yeol Park <peary2@gmail.com>
Cr-Commit-Position: refs/heads/master@{#616602}
6 files changed