Chrome version : 63.0.3219.0 (Official Build) 67ae3f5d8124e37b0fb71995bef29c9bd31ee9f4-refs/heads/master@{#502728} 32/64 bit
OS : Windows (7,8,10), Linux(14.04), Mac(10.12.6)

What steps will reproduce the problem?
1. Launch chrome, navigate to chrome://settings page and set 'Page zoom' level to 80%.
2. Now, by using Shift + Tab key, move focus on 'Font size' drop down list and observe the blue underline.

Actual Result : Blue underline does not change according to the zoom level. (i.e. an underline appears thick even for 80% zoom level)

Expected Result : An underline for drop down lists should change according to the current zoom level.

This is a regression issue broken in ‘M-58’ and below is the bisect info,

Using the per-revision bisect providing the bisect results,
Good build : 58.0.3011.0 (Revision: 449904).
Bad build : 58.0.3012.0 (Revision: 450199).

You are probably looking for a change made after 449942 (known good), but no later than 449943 (first known bad).

CHANGELOG URL: 
https://chromium.googlesource.com/chromium/src/+log/d6df828820be4b0f22b9bed959fb2bd93f84b331..934becac5daa91ea979fb66e4ae21761ca11ebc9

Suspect : https://chromium.googlesource.com/chromium/src/+/934becac5daa91ea979fb66e4ae21761ca11ebc9

@karlo : Could you please look into the issue, pardon me if it has nothing to do with your changes and if possible please assign it to concern owner.

Thank you!!
 

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	Actual_Result.mp4 1.2 MB View Download

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	Expected_Result.mp4 1013 KB View Download