Chrome Version: 71.0.3560.0
OS: Chrome

What steps will reproduce the problem?
(1) Run Chrome OS on Linux with remote debugging turned on.
(2) Open the Files app.
(3) Click on an image file (you might need to put an image file in your Downloads folder).
(4) Press space to bring up a "quick view".
(5) On workstation, go to the remote debugging page and inspect the page with "files_safe_img_webview_content.html".
(6) This should open a new tab with the image. Refresh the page by clicking the refresh icon on the browser (don't use Ctrl-R or the refresh icon in the inspector).

What is the expected result?
Nothing...the page should just refresh.

What happens instead?
In ChromeOS, the image will now have a white border around it, because the web contents have lost their transparency.

This is just one way to reproduce the issue, but the same thing happens on other apps that use transparency (e.g. virtual keyboard). Step (6) may not be the only way to trigger the bug, but it's the only way I found reliable.