The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cdf2fc776db0732e0fcf1f6b002464f489c5eec8

commit cdf2fc776db0732e0fcf1f6b002464f489c5eec8
Author: Kevin Strohbehn <ginko@google.com>
Date: Sat Aug 18 00:59:58 2018

Forward events to the apps grid view if they are in the same y-region

This allows for scrolling on the very edge to paginate the apps grid first,
before closing the launcher. By limiting the Y-region, you can still close
the launcher with a drag from the top.

Bug:  869642 
Change-Id: Ice9759a2e1dd0c3beb6019a00b570bba37e2a7a6
Reviewed-on: https://chromium-review.googlesource.com/1175454
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Weidong Guo <weidongg@chromium.org>
Commit-Queue: Kevin Strohbehn <ginko@google.com>
Cr-Commit-Position: refs/heads/master@{#584271}
[modify] https://crrev.com/cdf2fc776db0732e0fcf1f6b002464f489c5eec8/ash/app_list/views/apps_container_view.cc
[modify] https://crrev.com/cdf2fc776db0732e0fcf1f6b002464f489c5eec8/ash/app_list/views/apps_container_view.h
[modify] https://crrev.com/cdf2fc776db0732e0fcf1f6b002464f489c5eec8/ash/app_list/views/folder_background_view.cc

Fixed: This also included an update that allows for scrolling to occur while a folder is open. A followup bug for improving the animation was made: https://bugs.chromium.org/p/chromium/issues/detail?id=875133