The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/04ad2f701c01e367b9339794ba0ca4b7372e6274

commit 04ad2f701c01e367b9339794ba0ca4b7372e6274
Author: Dan Elphick <delphick@chromium.org>
Date: Sat Oct 14 05:57:43 2017

Add notifications for Background Fetches

Use offline_items_collection to display a notification (currently only
on Android) showing the title of the ongoing background fetch and its
origin.

The percentage shown is currently just based on the number of files
downloaded compared to the total number of files.

Also support cancelling/pausing/removing downloads through the
notification although this is not yet fed back to the javascript layer.
To simplify the code OnDownloadComplete is co-opted to pass failure
results as well as success by adding FailureReason to
BackgroundFetchResult.

Change-Id: I48ffa20dce3a6443bd219136a80dfe65f22f7375
Bug:  706829 
Reviewed-on: https://chromium-review.googlesource.com/690298
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: John Mellor <johnme@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#508930}
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/chrome/browser/background_fetch/background_fetch_delegate_impl.cc
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/chrome/browser/background_fetch/background_fetch_delegate_impl.h
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/browser/background_fetch/background_fetch_context.cc
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/browser/background_fetch/background_fetch_delegate_proxy.cc
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/browser/background_fetch/background_fetch_delegate_proxy.h
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/browser/background_fetch/background_fetch_delegate_proxy_unittest.cc
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/browser/background_fetch/background_fetch_job_controller.cc
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/browser/background_fetch/mock_background_fetch_delegate.cc
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/browser/background_fetch/mock_background_fetch_delegate.h
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/public/browser/background_fetch_delegate.h
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/public/browser/background_fetch_response.cc
[modify] https://crrev.com/04ad2f701c01e367b9339794ba0ca4b7372e6274/content/public/browser/background_fetch_response.h

Closing this because we have notifications on Android, and the desktop notification work is being tracked by 825924