r421578 shouldn't affect the dropdown menu, and I don't have Mac environment (I couldn't reproduce it on my Linux/Chrome OS)

mnikam@, how frequent can this be reproduced? Always?
If it reproduces reliably, is it possible to make the bisect range narrower?

With response to comment #1 :

Re-bisected the issue and below is the Narrow Bisect info : 

Narrow Bisect info :
https://chromium.googlesource.com/chromium/src/+log/a842013d816fd4a6c5855bffd65a0a7e27cfdd02..057643e80453b5733b4997258eee9227ef99ce45?pretty=fuller&n=100

Suspecting: r421098 from Narrow bisect

@calamity : Could you please help to reassign if your change is not the cause for this change.

Ok, this _was_ caused by my patch and I don't know why. I have a patch at https://codereview.chromium.org/2379243002/ which will fix it, but this is probably a rendering issue at heart.

Turning off the border-radius, z-index or overflow properties seems to fix this.

@chrishtr: any insights/suggestions?

This looks like a duplicate of  issue 651305 .

calamity@, given you can revert your change and solve the problem, I suggest we leave this open and I'll reach out to you when the underlying issue is fixed (i.e. when 651305 is fixed). Meanwhile, please continue to own the issue until you're patch lands, then assign to me.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/be74ba8f28e8d1371c2c5bdcc756ade34c47262e

commit be74ba8f28e8d1371c2c5bdcc756ade34c47262e
Author: dbeam <dbeam@chromium.org>
Date: Fri Sep 30 21:28:07 2016

MD Settings: disable border-radius when cards are expanded

Looks bad and is causing rendering issues.

R=michaelpg@chromium.org
BUG= 651344 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2388443003
Cr-Commit-Position: refs/heads/master@{#422226}

[modify] https://crrev.com/be74ba8f28e8d1371c2c5bdcc756ade34c47262e/chrome/browser/resources/settings/settings_page/settings_section.html

Note : Rechecked the above issue on latest canary chrome version : 55.0.2879.0 and the issue is not reproduced.

Thanks  mnikam@ for the update. Adding the verified label based on C#10. 

dbeam@: Please close the issue if there is no further work to be done here.

Thank you!

A friendly reminder that M55 Beta launch is coming soon! Your bug is labelled as Beta ReleaseBlock, pls make sure to land the fix ASAP. Thank you.