Resolve loose comparison in `removeDeclarationBlockBySelector()`

[JakeQZ]

This is a method of CSSList (which Document extends).

If it is not passed an array of Selector objects (directly, or indirectly via a DeclarationBlock), then it will construct a new array of Selector objects for use in comparison using ==, comparing the arrays.

AFAIK, any comparison involving objects, even if loose, requires the objects to be the same instances for a match. [Edit: I am seemingly proven wrong, though would like to understand the behaviour better.]

The only current tests for it inovle passing an existing DelcarationBlock; there are no tests that pass selectors as strings. [Edit: tests added in #1335.]

This may be a candidate for removal. @sabberworm, @oliverklee, WDYT? [Edit: it actually, surprisingly, works.]

[oliverklee]

Yes, makes sense. Kill it with fire!

[JakeQZ]

Yes, makes sense. Kill it with fire!

I'm pouring on water now.

Almost bewilderingly, it works. I added some tests - see #1335.

We will need to silence Stan another way. (If == is changed to ===, the tests I added will fail.)

I could not find any documentation on how array comparison is supposed to work with == and objects in the arrays.

[oliverklee]

Two arrays that have the same values, but different keys (or the values) in different order are not ===, but are ==. So we probably can === the corresponding array_values (or add a method hasOnlySelectors to DeclarationBlock, which I would consider to be the cleaner approach).

[JakeQZ]

It's comparing arrays of Selector objects, which aren't even the same objects. I don't know how the object comparison is done internally such that they are found to be equivalent.