1417569 - @media print rule does not work in WebExtension css files

Status: RESOLVED DUPLICATE of bug 1448507

(WebExtensions :: General, defect, P5)

Description

[Mykola]

Attachment: media-print-test.zip

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:59.0) Gecko/20100101 Firefox/59.0
Build ID: 20171115100050

Steps to reproduce:

See simple WebExtension in attachment.

Content script creates on every page 
<div class="test">This div must be invisible on print and print preview</div> 

Class "test" from injected media-print-test.css:
.test { /*Big red text in red border*/ }
@media print {
	.test { display: none; }
}

Load WebExtension as temporary addon.


Actual results:

On google.com we can see div with red border. Go to print preview. There is no border, but text is present.



Expected results:

Div "test" must be invisible on print preview.

P.S. Do not test this addon on Mozilla sites by reason of bug 1310082

Comment 1

[Jonathan Watt [:jwatt]]

Duplicate of bug 1448507. This was filed first, so normally I'd dup in the other direction, but the other bug now has info on what is causing this written up there.