As of https://codereview.chromium.org/2384273005, the arrow has been updated to a downwards pointing arrow and -webkit-appearance: none is being used, which I am guessing addresses the rounded corner.

I don't have my Mac with me today, but this might have already been addressed (will check tomorrow). FWIW this is how it is supposed to look http://imgur.com/a/gZZbJ.

Great. I've updated the title of the bug to reflect the color issue. Thanks!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ff0ec9bfafa871366d2407e9349685e97d784441

commit ff0ec9bfafa871366d2407e9349685e97d784441
Author: dpapad <dpapad@chromium.org>
Date: Wed Oct 05 22:12:10 2016

MD Settings: Adjust <select> focus color and bottom border radius.

BUG= 652914 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2400483002
Cr-Commit-Position: refs/heads/master@{#423312}

[modify] https://crrev.com/ff0ec9bfafa871366d2407e9349685e97d784441/chrome/browser/resources/settings/md_select_css.html

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ff0ec9bfafa871366d2407e9349685e97d784441

commit ff0ec9bfafa871366d2407e9349685e97d784441
Author: dpapad <dpapad@chromium.org>
Date: Wed Oct 05 22:12:10 2016

MD Settings: Adjust <select> focus color and bottom border radius.

BUG= 652914 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2400483002
Cr-Commit-Position: refs/heads/master@{#423312}

[modify] https://crrev.com/ff0ec9bfafa871366d2407e9349685e97d784441/chrome/browser/resources/settings/md_select_css.html

[Automated comment] removing mislabelled merge-merged-2840