robinroeper10@ Thanks for the issue.

Tested this issue on Windows 10 on the reported version 66.0.3359.117 and the latest Canary 68.0.3403.0 and unable to reproduce the issue by following the given steps above.

Scrolled for a while on a page and middle clicked on the mouse to activate the auto-scrolling. Cannot observe any issues while auto-scrolling through a website.
Attached is the screen cast for reference.

Request you to retry the issue on a new chrome profile without any flags/extensions and update the thread with the observations.

Thanks..

Deleted: 835314.webm 8.1 MB

	835314.webm 8.1 MB View Download

Hey all,

It looks like we may have a couple more reports as well of similar behavior:
- https://productforums.google.com/forum/#!msg/chrome/FWdpwVX4V7I/vTKqL2xvBAAJ
- https://listnr.corp.google.com/report/85272772133
- https://listnr.corp.google.com/report/85335290588

Thanks!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/71f099520097b050b6c9363391fde6c758e0aa9b

commit 71f099520097b050b6c9363391fde6c758e0aa9b
Author: sahel <sahel@chromium.org>
Date: Fri Apr 27 20:30:50 2018

Autoscroll has priority over wheel scrolling.

On autoscroll start the mouse_wheel_phase_handler_ ends the current
scrolling sequence(if such exists). While Autoscrolling wheel events
in the mouse wheel event queue are ignored and once autoscrolling ends
the mouse_wheel_event_queue resumes processing wheel events normally.

This change is identical to giving priority to touchscreen scrolling
over wheel scrolling and it is done to make sure that attempting to
wheel scroll during a middle click autoscroll doesn't cause unwanted GSB
/GSE generation.

Bug:  835314 
Test: *.TimerBasedLatchingBreaksWithAutoscrollStart
Change-Id: Id568ee2676a6dafc2705c144ea4d92d46311b788
Reviewed-on: https://chromium-review.googlesource.com/1011457
Commit-Queue: Sahel Sharifymoghaddam <sahel@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#554496}
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/input/mouse_wheel_event_queue.cc
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_impl.cc
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_view_android.cc
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_view_android.h
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_view_aura.cc
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_view_aura.h
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_view_aura_unittest.cc
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_view_base.cc
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_view_base.h
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_view_mac.h
[modify] https://crrev.com/71f099520097b050b6c9363391fde6c758e0aa9b/content/browser/renderer_host/render_widget_host_view_mac.mm

robinroeper10@ could you please check the latest Chrome Canary to see if the bug still happens there or not?

The fix is first landed in 68.0.3412.0

Great, thanks!

sahel@ Confirm that the bug has been fixed.

Tested on Chrome Canary Version 68.0.3416.0

Deleted comment #10 since it was wrong duplication.

 Issue 811156  has been merged into this issue.