Chrome Version: 71.0.3542.0 (Official Build) Revision	4097c6595e73c799040bc3a99bcfcc6adb178386-refs/branch-heads/3542@{#1} (32/64-bit)
OS: Windows(7,8,8.1 and 10) and Linux(14.04 LTS).

Pre-condition: Enable the flag 'Enable using the Google local NTP' and 'New Tab Page Background Selection' from chrome://flags/

What steps will reproduce the problem?
1. Launch Chrome, go to NTP and click on gear icon to open 'Customize this page' menu list
2. Select 'Chrome backgrounds' option from 'Customize this page' menu list (Select a Collection overlay will open).
3. Now press and hold the down arrow key so that vertical scroll-bar reaches to it's last postion and observe.

Actual: Down arrow of vertical scroll-bar doesn't get disabled.
Expected: Down arrow of vertical scroll bar should get disabled.

This is a regression issue broken in 'M-70' series and providing the bisect info below:

Good Build: 70.0.3532.0 (Revision: 585633)
Bad Build:  70.0.3533.0 (Revision: 586155)

You are probably looking for a change made after 585909 (known good), but no later than 585919 (first known bad).

CHANGE-LOG URL:
https://chromium.googlesource.com/chromium/src/+log/cedf15c7b4d8b44acefbb183334a1cb59a713965..7adb12c2303f1be21c3ef69ba92f0323ece71544

Suspecting: https://chromium.googlesource.com/chromium/src/+/cdfd0835f3bb7598748a5eff0b1ec368b64f0eb1

@sweilun: Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

NOTE:
1. Provided suspect through 'Chromium bisect' script because unable to perform bisect using 'per-revision' bisect script.
2. Tried performing 'per revision' bisect on multiple Windows and Linux machines but unable to perform the same since getting following error:
   (a) Error message on Windows and Linux OS : Unable to find locale data files
3. This issue is not reproducible on  Mac (10.12.6, 10.13.1, 10.13.6, 10.14) OS.
4. This issue is also reproducible on Dev #70.0.3534.4

Kindly review the attached screen-cast for reference.

Thank you.
 

Deleted: Actual behavior.mp4 1.0 MB

	Actual behavior.mp4 1.0 MB View Download

Deleted: Expected behavior.mp4 1.0 MB

	Expected behavior.mp4 1.0 MB View Download