Support ABP's CSS filter as an alias of :style()

[Yuki2718]

Prerequisites

• I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• This is NOT a YouTube, Facebook or Twitch report. These sites MUST be reported by clicking their respective links.
• This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• The issue is not present after disabling uBO in the browser.
• I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• uBO is the only extension.
• uBO uses default lists and settings.
• using a new, unmodified browser profile.

Description

Related to #3451
https://gitlab.com/eyeo/adblockplus/abc/webext-ad-filtering-solution/-/releases/1.4.0

A specific URL where the issue occurs.

NA

Steps to Reproduce

NA

Expected behavior

NA

Actual behavior

NA

uBO version

1.61.1b2

Browser name and version

Firefox 132.0.2

Operating System and version

Windows 10

[gorhill]

Should work with 1.61.1b3:

example.com#?#body {color: red;}

[Yuki2718]

Confirmed

[krystian3w]

Theoretically, Eyeo has pulled a trick where you can omit !important from their syntax because the ABP engine will add it:

https://help.adblockplus.org/adblock-plus-help-center/how-to-write-filters#Inline-CSS-styles

Fortunately, it's enough for the list creator to maintain their habit and add them. So the problem will only affect lists that optimize characters in the EasyList syntax and don't have a supplement for uBo.

https://github.com/easylist/easylist/blob/754e4809db36e7dbb26b8e4321bbe489506cdf28/easylist/easylist_specific_hide_abp.txt#L251-279 (some currently do not enforce !important, maybe they are 100% from uBo.txt and to avoid addressing in both files the newer ones already have it added).

[Yuki2718]

I guess the likelihood of an actual issue will be very rare. Most of CSS filters work even without !important, as a style inserted by an extension has higher priority. Sure, in some cases sites put !important. In that case not only uBO but also AdGuard apps will suffer. Maybe such cases should be handled by in-house filters.

[gorhill]

Also, it seems ABP's approach is to allow only one style property at a time, so if you want to modify three properties, you will need to create three filters. This needs confirmation but it's what I am understanding from their documentation.

[Yuki2718]

Maybe uBO can complement !important when converting the ABP style rules?