Auto merge of #14646 - canaltinova:origin-clean, r=jdm

Support origins in CSSOM stylesheets

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I still need to pass the origin clean flag to constructors. `style::stylesheets::Stylesheet` has an origin field but I don't think that's relevant.
I can get href in htmllinkelement.rs like this:
```rust
let element = self.upcast::<Element>();
let href = element.get_string_attribute(&local_name!("href"));
```
But I'm not sure how to proceed after here.
@Manishearth any opinions?

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- [X] These changes fix #14327 (github issue number if applicable).

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