Issue 803375 has been merged into this issue.

Assigning to Shakti to look today and coordinate with Joy when she gets back.

Actually the following CL is causing this issue on KitKat which was added recently.
https://chromium-review.googlesource.com/c/chromium/src/+/793831

This CL moves NotificationManger usage to use NotificationManagerCompat.
This is eventually causing an issue when we are building notification.

https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationService.java?rcl=4dbf36b9d88184677aa4aac9feb2f71686af7e1c&l=1080

If we comment out the setGroup() call, the bug is fixed. setGroup was added after KitKat, even then it should behave ideally as a noop in Kitkat. However when start using NotificationManagerCompat as in the above CL, this probably uncovers something incompatible and hence no notification shows up.

Is it worth it to talk to Android to make sure that NotificationManagerCompat works reasonably in KitKat instead of us going through and finding every place where there's a setGroup() call?

(Or at least to do this in addition to the changes that make sure things work for us?)

Patch reverted. 

Revert CL landed : 
https://chromium-review.googlesource.com/c/chromium/src/+/882481

We see issue in Chrome:65.0.3325.16  Device:Samsung Galaxy Note 3(SM-N900)/JSS15J

Your change meets the bar and is auto-approved for M65. Please go ahead and merge the CL to branch 3325 manually. Please contact milestone owner if you have questions.
Owners: cmasso@(Android), cmasso@(iOS), bhthompson@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Any update on #4? Was this indeed a bug in the support library or was it caused by Chrome code using a mixture of NotificationManager and NotificationManagerCompat?

(we're thinking of moving to Notification Compat methods with web notifications and would be helpful to be aware of any footguns)

awdf@ - For this case, we were using NotificationManagerCompat.notify() to notify and NotificationCompat.Builder.setGroup() to set a group. Ideally this should have worked and android should have ignored the setGroup call for KitKat.
A temporary workaround (https://chromium-review.googlesource.com/c/chromium/src/+/874520) fixes that, but we decided to revert the original CL. I think this sounds to me more like an android bug.

Are you planning to merge this into M65?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2e1ca3cff62a6153490a57f96eda8dbb59037a85

commit 2e1ca3cff62a6153490a57f96eda8dbb59037a85
Author: Shakti Sahu <shaktisahu@chromium.org>
Date: Fri Feb 09 20:27:17 2018

Revert "Some NotificationManager/Notification.* --> NotificationManagerCompat.*"

This reverts commit 2b484b1118316bd52495ed2cfa45c78d28ba8857.

Reason for revert: This CL causes missing notifications (crbug/803258).

Original change's description:
> Some NotificationManager/Notification.* --> NotificationManagerCompat.*
>
> Patch is enabling using NotificationManagerCompat.IMPORTANCE_LOW|HIGH
> instead of Notification.PRIORITY_LOW|HIGH (deprecated with Android O)
>
> and is replacing NotificationManager with NotificationManagerCompat
> in related files
>
> Bug:
> Change-Id: I16bb24b692846d2ef3fbf791e2a36de901e5d578
> Reviewed-on: https://chromium-review.googlesource.com/793831
> Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
> Reviewed-by: Min Qin <qinmin@chromium.org>
> Commit-Queue: Marcin Wiącek <marcin@mwiacek.com>
> Cr-Commit-Position: refs/heads/master@{#528932}

TBR=marcin@mwiacek.com, mlamouri@chromium.org, qinmin@chromium.org, shaktisahu@chromium.org


(cherry picked from commit f6e20f64fb9d6bc4045aea5b24de4ab0b8bfb455)

Change-Id: I341f757ab179629cada7f68364df99010f08055d
Reviewed-on: https://chromium-review.googlesource.com/882481
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#531593}
Bug:  803258 
Reviewed-on: https://chromium-review.googlesource.com/912311
Cr-Commit-Position: refs/branch-heads/3325@{#411}
Cr-Branched-From: bc084a8b5afa3744a74927344e304c02ae54189f-refs/heads/master@{#530369}
[modify] https://crrev.com/2e1ca3cff62a6153490a57f96eda8dbb59037a85/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationFactory.java
[modify] https://crrev.com/2e1ca3cff62a6153490a57f96eda8dbb59037a85/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationService.java
[modify] https://crrev.com/2e1ca3cff62a6153490a57f96eda8dbb59037a85/chrome/android/java/src/org/chromium/chrome/browser/media/MediaCaptureNotificationService.java
[modify] https://crrev.com/2e1ca3cff62a6153490a57f96eda8dbb59037a85/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappActionsNotificationManager.java

hmmm, just for FYI: there is prepared new patch for Notifications (different from reverted one), feel free to join discussion: https://chromium-review.googlesource.com/c/chromium/src/+/888748