The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/60036df9cee4317b4c271b3b3e43c536d45ba1dd

commit 60036df9cee4317b4c271b3b3e43c536d45ba1dd
Author: Anita Woodruff <awdf@chromium.org>
Date: Wed May 02 12:41:14 2018

[Notifications] Postpone callback on non-persistent notification close

The callback should only be called after the notification close event
has completed. This change postpones execution of the callback until
the proper time.

I had to add some workarounds because for some reason it seems the
callback does not now get called from tests.

R=peter@chromium.org

Bug:  787459 
Change-Id: I4450d54894f79f3e83581686965a328ef961e383
Reviewed-on: https://chromium-review.googlesource.com/1018461
Commit-Queue: Anita Woodruff <awdf@chromium.org>
Reviewed-by: Finnur Thorarinsson <finnur@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Anita Woodruff <awdf@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555361}
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/chrome/browser/notifications/non_persistent_notification_handler.cc
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/chrome/browser/notifications/stub_notification_display_service.cc
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/content/browser/notifications/blink_notification_service_impl.cc
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/content/browser/notifications/blink_notification_service_impl_unittest.cc
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/content/browser/notifications/notification_event_dispatcher_impl.cc
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/content/browser/notifications/notification_event_dispatcher_impl.h
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/content/browser/notifications/notification_event_dispatcher_impl_unittest.cc
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/content/public/browser/notification_event_dispatcher.h
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/third_party/blink/public/platform/modules/notifications/notification_service.mojom
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/third_party/blink/renderer/modules/notifications/notification.cc
[modify] https://crrev.com/60036df9cee4317b4c271b3b3e43c536d45ba1dd/third_party/blink/renderer/modules/notifications/notification.h

Re-opening because actually this still needs implementing for the 'click' events. 

Re-assigning to peter as he's implementing click acks as part of https://chromium-review.googlesource.com/c/chromium/src/+/1057631 for Issue 442141

Closing as click acks were implemented as part of https://chromium-review.googlesource.com/1057631 ('Create a new tab when the user activates orphaned non-persistent notifications')