Chrome Version: 51.0.2704.4 Revision 5bcb06bd733f10474ea2f719aa594b13883a393e-refs/branch-heads/2704@{#6}(32/64 bit)
OS: Windows

Steps:
1. Launch Chrome and open Devtool on NTP.
2. Press F1 to open setting and select 'Dark' from Theme drop-down.
3. Now try to scroll the styles and computed tabs by hovering the mouse over the scrollbar via mouse wheel.
4. Observe.

Actual: Unable to scroll the tabs through mouse wheel on hovering the mouse over scrollbar after applying Dark theme.

Expected: Should be able to scroll the tabs through mouse wheel after applying Dark theme.

This is a regression issue broken in M-49, below is bisect info.

Good build: 49.0.2576.0
Bad build: 49.0.2577.0

Narrow bisect: 
https://chromium.googlesource.com/chromium/src/+log/fec83354cf13825d8dd7fc9290853ff922d0ee1c..0cd7eeec54a1bc80b870a2a5f3cc78f2de83e955?pretty=fuller&n=100

Suspecting: r361956 ?

Please help to reassign if your change is not the cause for this issue.


 

Deleted: Actual_video.mp4 674 KB

Actual_video.mp4 674 KB Download

Deleted: Expected_result.mp4 654 KB

Expected_result.mp4 654 KB Download