GitLab

Rename ArcWallpaperHandler to ArcWallpaperService and implement it as an ArcService, which handles WallpaperManager API from Android.

Test=Manually open PickMyWallpaper app and set wallpaper
Test=run cts android.content.cts.ContextWrapperTest

Bug=642465

Review-Url: https://codereview.chromium.org/2264743002
Cr-Commit-Position: refs/heads/master@{#417428}