Chrome version : 61.0.3163.100 (Official Build) 57c9d07b416b5a2ea23d28247300e4af36329bdc-refs/branch-heads/3163@{#1250} 32/64 bit
OS : Windows(7,8,10)

What steps will reproduce the problem?
1. Launch chrome, navigate to chrome://settings and set 'Page zoom' level to 80%.
2. Now scroll down the page completely, middle click on the page and try to autoscroll settings page upwards.
3. Observe.

Actual Result : Autoscroll does not work on settings page when page zoom level is set to 80%.

Expected Result : Autoscroll should keep working even when zoom level is set to other custom value.

This is a regression issue broken in ‘M-61’ and using the per-revision bisect providing the bisect results,
Good build : 61.0.3132.0 (Revision : 479901)
Bad build : 61.0.3133.0 (Revision : 480259)

You are probably looking for a change made after 479930 (known good), but no later than 479931 (first known bad).

CHANGELOG URL: 
https://chromium.googlesource.com/chromium/src/+log/9ede2cde5727eecdb377b57b32c5226d1d41c8ce..5971e47dc08dbb773f58fd6fb13b1df7917fd295

Suspect : https://chromium.googlesource.com/chromium/src/+/5971e47dc08dbb773f58fd6fb13b1df7917fd295

@aelias : Could you please look into the issue, pardon me if it has nothing to do with your changes and if possible please assign it to concern owner.

Note : Issue is not reproducible on Mac(10.12.6) and Linux(14.04 LTS), since middle click autoscroll feature is not available in these OS.

Thank you.
 

Deleted: Actual_Autoscroll.mp4 1.1 MB

	Actual_Autoscroll.mp4 1.1 MB View Download

Deleted: Expected_Autoscroll.mp4 1.2 MB

	Expected_Autoscroll.mp4 1.2 MB View Download