Create a new filter class for CSS property filters

[trev]

Background

CSS property filters will use a syntax compatible with element hiding filters: example.com##.foo > [-abp-properties='|background-image: url(data:*)']. However, the handling will be very different, meaning that they need their own class.

What to change

Create a new class CSSPropertyFilter extending ElemHideBase. This class should have additional properties selectorPrefix and selectorSuffix - substrings of the selector, before and after the -abp-properties clause respectively. It should also have a lazily resolved regexp property, similarly to RegExpFilter. The logic for converting abp-properties value into a regular expression should be shared between CSSPropertyFilter and RegExpFilter.

ElemHideBase.fromText() should be extended to recognize CSS property filters and return an instance of the correct class. Optional: verify that there is at least one positive entry in the domains list and return InvalidFilter if there is none (only if the performance won't suffer).

[trev]

Heh, Trac created two identical issues, see #2390.