Removed the session history from BrowsingContext.
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The session history is stored in the constellation and accessed via the `History` object, so `BrowsingContext` doesn't need to track it.
cc @jdm @ConnorGBrewster @Ms2ger
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Removed duplicate #![feature(plugin)]
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Removed duplicate ` #![feature(plugin)]` from two files.
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- [ ] These changes fix#13581 (github issue number if applicable).
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Start simplifying FFI ownership sugar
This is step one of a series of changes planned to make the ownership sugar easier to use. This was blocked on #13038
*very* unsure about second commit. Don't like the thought of accepting types with destructors over FFI. Probably will revert it. Leaving it in for now in case you have some insight.
Eventually at least for the borrowed stuff I want to use T directly (because the crates are merged now), instead of the fake void types. Perhaps for the others too. I might include those changes in this PR -- was originally planning to but I realized that these steps could be split out.
Tentative plan for `Owned` (assuming it's not removed) is to have `Owned<T> <-> Box<T>` (same `T`, no "FFI type") conversions. We will only use ownership wrapper types for things with destructors, and try to keep the conversion simple. I'm envisioning a couple methods for arc/strong and a few more for box/owned. We may need to introduce new wrapper types for gecko-side managed objects (`RefPtr<T>`, `UniquePtr<T>`) but that should be all the wrapper types we have in the ownership sugar.
This PR relies on the guarantee that `Option<&T>` and `Option<Box<T>>` are pointer-sized via the `NonZero` optimization. I am now less unconvinced that this is a good idea 😉.
r? @emilio
cc @mystor
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Add to_css_single_value for serializing a single PropertyDeclarationBlock
(fixes#13423)
r? @birtles
This needs to take the name of the property in question as input so that it can figure out which shorthand to serialize to (if any), since some props are part of multiple shorthands (and you need a way to distinguish between the lone value and the shorthand). I can tweak this to accept an `Option<Shorthand>` in case you only want to pass in the property name for shorthands.
In case you don't want to handle shorthands at all, we probably don't need this method at all, since you can just assert that there's a single field and serialize that.
Also, is `!important` involved here?
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