Replacing downloads backend with DownloadOfflineContentProvider

This CL attempts to replace the downloads backend for UI with offline
content provider behind a feature flag. The UI affected include
notifications, new download home and download infobar.

Bug : 939634

Change-Id: I207fced84a202c2ed8dcfa5c963993d6f4af40a7
Commit-Queue: Shakti Sahu <>
Reviewed-by: David Trainor <>
Cr-Commit-Position: refs/heads/master@{#638931}
20 files changed