Able to reproduce the issue on reported chrome version 63.0.3239.132 and on the latest canary 65.0.3322.0  using windows 10  surface pro.
Note: Issue is not seen on Mac 10.13.1 and Ubuntu 14.04

Bisect Info:
==================
Good Build: 59.0.3067.0(463157)
Bad Build:  59.0.3068.1(463474)

You are probably looking for a change made after 463188 (known good), but no later than 463195 (first known bad).
CHANGELOG URL:
    https://chromium.googlesource.com/chromium/src/+log/0bd89391dc79ae15c314d632f5829b0d430cf9af..5136241948671b538965c783e8aee27e88037aa9
Note: Could not provide hasbisect-per-revision as we are getting perf errors while builds are invoking.

Suspecting: https://chromium.googlesource.com/chromium/src/+/112094796a99ff35f551467912814d08935b6055
Reviewed-on: https://codereview.chromium.org/2810583002

tkent@: Please feel free to re-assign if it is not related to your change.

Thanks!

Thank you for verifying this issue so fast!!!

As for the mentioned keyboard error, i am actually test with different Chrome and Windows versions, probably i will open an issue for this.

This happens on touch-enabled devices, not HiDPI. Basically this works as intended now, however we might be able to improve behavior.  e.g. Enlarge lines only if the popup is opened by touch.

I cannot follow your comment or i don't understand what you say.

It does not matter whether i open the dropdown on the Surface Tablet by pen, by finger or with connected USB mouse - i get always the huge space between the dropdown items with the current chrome browser version.

Attached surface_59_0_3068_0__463188.png shows the same sample with Chrome version 59.0.3068.0 (463188) on Surface tablet - The space between the dropdown items looks just right for me, also the scrollbar size is fine. I would expect about the same spacing between the dropdown items on any device with any resolution and any Windows scale setting.

new_pc.png shows the sample on PC with 1920x1080 resolution - It looks fine with current Chrome version on PC while on Surface tablet it looks odd.

I have ordered now a non-DPI tablet with 1280x800 pixel (Surface has 2736x1824), will see how it looks there.

Deleted: surface_59_0_3068_0__463188.png 214 KB

	surface_59_0_3068_0__463188.png 214 KB View Download

Deleted: new_pc.png 10.3 KB

	new_pc.png 10.3 KB View Download

tkent@: 
I think i got it now, the increased space between the dropdown items on touch devices was done because a change/feature request, maybe to make it a bit more unlikely to pick the wrong item when selecting an item with the finger?

Do you plan then to add this extra space also in listboxes?

It would be great if you can change it this way:
- Increased spacing only when clicked with the finger (not when clicked with pen or mouse)
- I can understand that it may make sense to have increased space between the items when the user uses his finger... a bit more space seems ok to me, but maybe a bit less than it is now, so it looks a bit better.
- Make it also an option in the browser settings, so the user can customize this behaviour

I checked this now also on device with no windows scaling needed.
You are absolutely correct, it seems to happen only on touch devices.
For my smell the space between the items is by far too much... if one needs so much space to pick the right item... the browser on touch devices is not really usable at all for those guys.
This is just only my subjective opinion.

 Issue 788109  has been merged into this issue.