Chrome Version : 69.0.3457.2 (Official Build) (64-bit) (cohort: Stable) Revision: 9c525f32d5d7caf55004d2318ac334580d63a579-refs/branch-heads/3457@{#5}
OS: Win (7,8,8.1,10,  )Mac OS X(10.12.6,10.13.1,10.13.6).

Steps to reproduce:
1. Launch Chrome and open dev tools on NTP.
2. Click on 'Toggle device toolbar', Select a device from dropdown, Click on 'More options' button and Select 'Show device option'.
3. Perform an 'Audit'(on completion) then click on 'Customize and control DevTools' option and select 'Settings' options of dev tools .
4. Change the theme to 'Dark' and observe.

Actual:  Device frame disappears when the theme is changed to 'Dark'.
Expected: Device frame should not disappear when the theme is changed.

This is regression issue broken in ‘M-65’ and below is the  has-bisect per-revision info:
Good Build: 65.0.3295.0 (Revision:524285)
Bad Build: 65.0.3296.0 (Revision:524554)

You are probably looking for a change made after 524288 (known good), but no later than 524290 (first known bad).
CHANGELOG URL:
The script might not always return single CL as suspect as some perf builds might get missing due to failure.
https://chromium.googlesource.com/chromium/src/+log/c03976e35fab4151673031e792a20c40813876b2..4cbe8ee5fd2f658f07c3a7d2f959f3cc8e2facb2

Suspecting: https://chromium.googlesource.com/chromium/src/+/9f8d4632b417d2f4fa8216f9be3a19a16554806c

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

Note: Issue is also seen on M67 Stable build #67.0.3396.87 and M68 Beta build #68.0.3440.25


Thank You!
 

Deleted: Actual Result(DevTools).mp4 2.1 MB

	Actual Result(DevTools).mp4 2.1 MB View Download

Deleted: Expected Result(DevTools).mp4 2.5 MB

	Expected Result(DevTools).mp4 2.5 MB View Download