Chrome version: 73.0.3632.0 (Official Build) Revision 914f5b8f721ff5a734bb22a96363191c20c8c3f2-refs/branch-heads/3632@{#1}(32/64-bit)
OS: Windows (7,8,8.1,10)

What steps will reproduce the problem?
1. Launch chrome,navigate to NTP and open devtools
2. Now go to 'Memory' section and press 'Esc' key to open 'Console' drawer and then hover mouse over '>>' chevron icon and observe
 
Actual: Scroll bar disappears on hovering mouse over '>>' chevron icon and removing mouse from it
Expected: Scroll bar shouldn't disappear on hovering mouse over '>>' chevron icon and removing mouse from it
 
This is regression issue, broken in ‘M 69’ and below is the bisect info :
Good build: 69.0.3489.0  (Revision: 574446).
Bad build: 69.0.3491.0 (Revision: 575129).

You are probably looking for a change made after 574888 (known good), but no later than 574889 (first known bad).

CHANGE-LOG URL:

The script might not always return single CL as suspect as some perf builds might get missing due to failure.

https://chromium.googlesource.com/chromium/src/+log/bdb7c6bf6d378e95ddeb81014e30bb19cdd87c86..0670e881945cb0c5f3c49ab55f7f96007472c0e3

Suspecting: https://chromium.googlesource.com/chromium/src/+/0670e881945cb0c5f3c49ab55f7f96007472c0e3

@kylixrd: 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.

Kindly review the attached screen-cast for reference.

Note:
1.Issue is not seen on Mac(10.12.6,10.13.1,10.13.6) and Linux (14.04 LTS) OS
2.Issue is only reproducible for device monitors with screen resolution 1280 X 1024
3.Able to reproduce issue on Stable #71.0.3578.80, Beta#71.0.3578.80, Dev# 72.0.3626.7

Thank you.
 

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