Fixes#7867 (and probably several other iframe bugs).
When collecting layers for children of a pipeline, pass through the current
subpage pipeline recursively. This prevents descendany layers (such as scroll
layers) from being collected and re-created on the subsequent paint.
Update URL-related interfaces and their tests up to spec
The URL spec recently changed and the variour "mixins" interfaces are gone,
this commit updates our code and WPT accordingly.
The new expected failures related to HTMLAnchorElement and HTMLAreaElement's
attributes are due to their moving to the HTMLHyperLinkElementUtils interface,
which is not anymore in a separate `<script class=untested>` element.
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The URL spec recently changed and the variour "mixins" interfaces are gone,
this commit updates our code and WPT accordingly.
The new expected failures related to HTMLAnchorElement and HTMLAreaElement's
attributes are due to their moving to the HTMLHyperLinkElementUtils interface,
which is not anymore in a separate <script class=untested> element.
Clarify some code in do_create_interface_objects
rval.get() is believed to be always null upon entering this function.
This assumption is verified by the added assertion.
It makes more sense to move the block of code that was moved inside
the if statement which is the only place where it can be initialized.
Fixes#7941.
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Implement Deref<Target=T> for JS<T> where T: Reflectable
We can only borrow `JS<T>` from rooted things, so it's safe to deref it.
The only types that provide mutable `JS<T>` things are `MutHeap<JS<T>>` and
`MutNullableHeap<JS<T>>`, which don't actually expose that they contain
`JS<T>` values.
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