The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8c577b8ef4675ae2438197941561a4c401a61283

commit 8c577b8ef4675ae2438197941561a4c401a61283
Author: Chris Pickel <sfiera@chromium.org>
Date: Wed Sep 06 14:56:39 2017

Introduce callback-based LogoService interface

Provide versions for both encoded and decoded logos. Each version takes
two callbacks: one for the cached logo and one for the encoded logo.
They are called 0 or 1 times, which is at least simpler than the
observer interface's 0-2 times.

For now, the callback interface is implemented using the observer
interface (and the same self-deleting style of observer), but that can
change easily when clients use the callback interface instead.

Bug:  761824 
Change-Id: I2e9ac76a0b9ead5084711e643764731a768f9f46
Reviewed-on: https://chromium-review.googlesource.com/649647
Commit-Queue: Chris Pickel <sfiera@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#499964}
[modify] https://crrev.com/8c577b8ef4675ae2438197941561a4c401a61283/components/search_provider_logos/logo_common.h
[modify] https://crrev.com/8c577b8ef4675ae2438197941561a4c401a61283/components/search_provider_logos/logo_service.cc
[modify] https://crrev.com/8c577b8ef4675ae2438197941561a4c401a61283/components/search_provider_logos/logo_service.h
[modify] https://crrev.com/8c577b8ef4675ae2438197941561a4c401a61283/components/search_provider_logos/logo_service_unittest.cc
[modify] https://crrev.com/8c577b8ef4675ae2438197941561a4c401a61283/components/search_provider_logos/logo_tracker.cc
[modify] https://crrev.com/8c577b8ef4675ae2438197941561a4c401a61283/components/search_provider_logos/logo_tracker.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/67e0b77d9272fd476d0288d4bc58da5626a3d9ab

commit 67e0b77d9272fd476d0288d4bc58da5626a3d9ab
Author: Chris Pickel <sfiera@chromium.org>
Date: Mon Sep 18 16:55:18 2017

LogoTracker: use callbacks for everything

In order to mimic the existing LogoObserver interface, add a |type|
argument to distinguish reasons for the callback: the observer is
interested in FETCHED and CLEARED callbacks, but not DISABLED,
REVALIDATED, FAILED, or CANCELED.

Simplify LocalNTPSource by letting LogoTracker do all the multiplexing.
Add the data: URL for the image to the response.

Bug:  761824 
Change-Id: Iefe2e2b19ebd940abe76581c2e3691307bdc652e
Reviewed-on: https://chromium-review.googlesource.com/662783
Commit-Queue: Chris Pickel <sfiera@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502593}
[modify] https://crrev.com/67e0b77d9272fd476d0288d4bc58da5626a3d9ab/chrome/browser/search/local_ntp_source.cc
[modify] https://crrev.com/67e0b77d9272fd476d0288d4bc58da5626a3d9ab/components/search_provider_logos/logo_common.cc
[modify] https://crrev.com/67e0b77d9272fd476d0288d4bc58da5626a3d9ab/components/search_provider_logos/logo_common.h
[modify] https://crrev.com/67e0b77d9272fd476d0288d4bc58da5626a3d9ab/components/search_provider_logos/logo_service.cc
[modify] https://crrev.com/67e0b77d9272fd476d0288d4bc58da5626a3d9ab/components/search_provider_logos/logo_service.h
[modify] https://crrev.com/67e0b77d9272fd476d0288d4bc58da5626a3d9ab/components/search_provider_logos/logo_service_unittest.cc
[modify] https://crrev.com/67e0b77d9272fd476d0288d4bc58da5626a3d9ab/components/search_provider_logos/logo_tracker.cc
[modify] https://crrev.com/67e0b77d9272fd476d0288d4bc58da5626a3d9ab/components/search_provider_logos/logo_tracker.h