Chrome Version: 63.0.3233.0
OS: Android 6.0.0; Nexus 5X

What steps will reproduce the problem?
(1) Restart Chrome (start for first time / chrome://inducebrowsercrashforrealz)
(2) Press and hold to download an offline page.
(3) Press cancel on the download notification.

What is the expected result?
The download is cancelled--it does not show up as a notification again or show up in Downloads Home.

What happens instead?
The download notification disappears so it looks like it was cancelled, but reappears later as successful download notification (meaning it was downloading in the background).

This happens for cancelling as well as pausing.
After navigating to Downloads Home and then trying to do this again, the cancel/pause works as intended.
This is not replicable on not offline pages downloads.

Here is a video: https://drive.google.com/a/google.com/file/d/0BwltPzKKkOFqX1EwQk1Nby1iQWc/view?usp=sharing