Ginko, you're most familiar with this (you modified the gesture drag code to fix  issue 869642 . Can you investigate this?

Picking this up

Believe not the false news posted above.
It is I, ginko, picking this up.

TY sir

Okay, it looks like pagination controller won't handle a scroll begin if it occurs off-axis, which makes sense I suppose.

That being said, I opened a CL that lets apps grid just mark scroll begins as handled. (The few cases we want them to fall through are already handled before this)

newcomer@, do you actually want this merged back to 72? My guess is that this has been around for a minute, considering it was part of pagination controller

If it's not a regression, lets push to M-73. 

This definitely is a polish task, which we are prioritizing along with a11y this milestone, so lets keep the P-1.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5136abe4428e487d5697121d7572eb2f52d923d0

commit 5136abe4428e487d5697121d7572eb2f52d923d0
Author: Kevin Strohbehn <ginko@google.com>
Date: Mon Dec 17 20:08:40 2018

Prevent scroll events over app grid from falling through

Bug:  914025 
Change-Id: Ic714a6586b0c183f493c0da08e8383decff0ed68
Reviewed-on: https://chromium-review.googlesource.com/c/1379315
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Kevin Strohbehn <ginko@google.com>
Cr-Commit-Position: refs/heads/master@{#617200}
[modify] https://crrev.com/5136abe4428e487d5697121d7572eb2f52d923d0/ash/app_list/views/apps_grid_view.cc

Similar issues in peeking launcher and shelf tracked in a follow up:

 https://crbug.com/915784