GitLab

cros: Some cleanup in ash::WallpaperController

1) Moved public functions (which don't have to be public) to private
   or anonymous namespace. (During the refactoring these functions
   were made public in order to be used by //chrome).

2) Does not change any logic.

3) May need a follow-up CL to make the anonymous namespace functions to
   a separate file to make the class slimmer.

Bug: NONE
Change-Id: Ib67016cef0e8654ed8b8a674c24118a7f2f9b519
Reviewed-on: https://chromium-review.googlesource.com/1111571Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569774}