The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/57b0df8de3bc9762b900dcff3c517a131388b599

commit 57b0df8de3bc9762b900dcff3c517a131388b599
Author: Wenzhao Zang <wzang@chromium.org>
Date: Wed Jan 03 09:03:48 2018

wallpaper refactoring: Delete UpdateWallpaper in WallpaperDelegate

Previously, UpdateWallpaper() is needed in the WallpaperDelegate
interface because it relies on Chrome to set the correct image. After
everything is migrated, it no longer needs to call into Chrome.
(Eventually WallpaperDelegate will be deleted as well.)

All the tests in |wallpaper_manager_browsertest.cc| have been migrated
(some of them are deleted because they have been disabled for a long
time). But there is some untested code path in wallpaper_manager and
we'll add more tests in follow-up CLs.

TBR=oshima@chromium.org

Bug:  779221 ,  794725 
Change-Id: I81b0a0b6b2a96423a1191054e154761b10304382
Reviewed-on: https://chromium-review.googlesource.com/826325
Reviewed-by: Wenzhao (Colin) Zang <wzang@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526654}
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/default_wallpaper_delegate.cc
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/default_wallpaper_delegate.h
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/wallpaper/test_wallpaper_delegate.cc
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/wallpaper/test_wallpaper_delegate.h
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/wallpaper/wallpaper_controller.cc
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/wallpaper/wallpaper_controller.h
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/wallpaper/wallpaper_controller_unittest.cc
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/wallpaper/wallpaper_delegate.h
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/wallpaper/wallpaper_delegate_mus.cc
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/ash/wallpaper/wallpaper_delegate_mus.h
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/chrome/browser/chromeos/background/ash_wallpaper_delegate.cc
[delete] https://crrev.com/5ac59e663d764a3257c8a038a364d4cd578b4ef4/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager_browsertest.cc
[modify] https://crrev.com/57b0df8de3bc9762b900dcff3c517a131388b599/chrome/test/BUILD.gn