Adjusting priority since it's a cleanup task and is unassigned.

Clean-up tasks don't need a target milestone.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0d3a5d132af98a9f373379208150a5eb5819d175

commit 0d3a5d132af98a9f373379208150a5eb5819d175
Author: Yeol <peary2@gmail.com>
Date: Fri Dec 07 10:00:43 2018

Merged LogoService and LogoTracker.

LogoTracker is now an implementation detail of LogoService.
In order to simplify things further,
its implementation was moved inside LogoService.

Bug: 761829
Change-Id: I33e5ab909e3f66aec31546bb1833069f973216c9
Reviewed-on: https://chromium-review.googlesource.com/c/1349511
Reviewed-by: Ramin Halavati <rhalavati@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Yeol Park <peary2@gmail.com>
Cr-Commit-Position: refs/heads/master@{#614651}
[modify] https://crrev.com/0d3a5d132af98a9f373379208150a5eb5819d175/components/search_provider_logos/BUILD.gn
[modify] https://crrev.com/0d3a5d132af98a9f373379208150a5eb5819d175/components/search_provider_logos/fixed_logo_api.h
[modify] https://crrev.com/0d3a5d132af98a9f373379208150a5eb5819d175/components/search_provider_logos/logo_service_impl.cc
[modify] https://crrev.com/0d3a5d132af98a9f373379208150a5eb5819d175/components/search_provider_logos/logo_service_impl.h
[delete] https://crrev.com/3f353c8108d3c22e651c2deabc9a1597cbebcc5e/components/search_provider_logos/logo_tracker.cc
[modify] https://crrev.com/0d3a5d132af98a9f373379208150a5eb5819d175/components/search_provider_logos/logo_tracker.h
[modify] https://crrev.com/0d3a5d132af98a9f373379208150a5eb5819d175/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/0d3a5d132af98a9f373379208150a5eb5819d175/tools/traffic_annotation/summary/annotations.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9a98a3afea823f2810ca00d083ed273f336b07ec

commit 9a98a3afea823f2810ca00d083ed273f336b07ec
Author: Yeol <peary2@gmail.com>
Date: Fri Dec 14 06:42:08 2018

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}
[modify] https://crrev.com/9a98a3afea823f2810ca00d083ed273f336b07ec/chrome/browser/android/logo_bridge.cc
[modify] https://crrev.com/9a98a3afea823f2810ca00d083ed273f336b07ec/chrome/browser/search/local_ntp_source.cc
[modify] https://crrev.com/9a98a3afea823f2810ca00d083ed273f336b07ec/components/search_provider_logos/BUILD.gn
[rename] https://crrev.com/9a98a3afea823f2810ca00d083ed273f336b07ec/components/search_provider_logos/logo_observer.h
[modify] https://crrev.com/9a98a3afea823f2810ca00d083ed273f336b07ec/components/search_provider_logos/logo_service_impl.cc
[modify] https://crrev.com/9a98a3afea823f2810ca00d083ed273f336b07ec/components/search_provider_logos/logo_service_impl_unittest.cc