Thanks for filing the issue!

Unable to reproduce the issue on reported chrome version 64.0.3282.167 and on the latest canary 66.0.3350.0 using Mac with the below mentioned steps.
1. Launched Chrome
2. Inspected an element on a web page
3. Typed "dis", when the inspector forecasted "display" pressed Tab.
We didn't observe any input field with two empty lines. Attaching the screen cast of the same.

@Reporter: Could you please check the screen cast and let us know if we have missed anything while reproducing the issue. Any further inputs from your end helps us.

Deleted: 813421.mp4 3.4 MB

	813421.mp4 3.4 MB View Download

Hello,

thanks for the fast response. Your screen cast looks exactly the way it should work. Sadly, it's not the same behaviour in my case on my Mac. Did you see my gif? Any suggestions what to do to fix it?

Deleted: bug.gif 294 KB

	bug.gif 294 KB View Download

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

@Reporter: Thanks for your confirmation about the screen cast provided by us in comment#2. We recommend you to check the same issue in a clean/new profile without any extensions and apps installed. Please let us know if the issue still persists even after checking in a clean/new profile.

Steps to create a new profile:
1. Launch chrome -> chrome://settings -> Manage other people -> Click on add person -> Click on Add.

Thanks!

Seen it several times as well.

++Additional info @Comment#2,
Checked the issue on Mac 10.13.1 .

Thanks!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f481fed33c537130afc8f4500bb2baa740c4f6d8

commit f481fed33c537130afc8f4500bb2baa740c4f6d8
Author: Joel Einbinder <einbinder@chromium.org>
Date: Wed May 30 01:16:16 2018

DevTools: Consume newline after selecting suggestion in StylesSidebar

When selecting name suggestions with enter, a newline could be added
into the newly created value field.

Bug:  813421 
Change-Id: I37ac4fc9e6ac6c299c0b07c6ecf7f41f54548d42
Reviewed-on: https://chromium-review.googlesource.com/956315
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Joel Einbinder <einbinder@chromium.org>
Cr-Commit-Position: refs/heads/master@{#562684}
[modify] https://crrev.com/f481fed33c537130afc8f4500bb2baa740c4f6d8/third_party/blink/renderer/devtools/front_end/elements/StylesSidebarPane.js

@Reporter: As we are unable to reproduce(...comment#2) the issue from our end on reported chrome version 64.0.3282.167 using Mac 10.13.1. The issue seems to be fixed in 69.0.3445.0 as per comment#8. Could you please check the same in latest canary and let us know the behaviour. Please find the below link to download the latest chrome versions.
https://www.chromium.org/getting-involved/dev-channel

Thanks!

 Issue 795727  has been merged into this issue.

 Issue 864579  has been merged into this issue.