Mark dictionaries containing GC values as must_root, and wrap them in
RootedTraceableBox in automatically-generated APIs. To accommodate
union variants that are now flagged as unsafe, add RootedTraceableBox
to union variants that need to be rooted, rather than wrapping the
entire union value.
A media element can delay the document's load event without having a resource URL,
and it can even block it while being inserted into a different document AFAIK.
Remove sources of panic when laying out an iframe without a nested browsing context
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At the moment, layout panics if it discovers an iframe without a nested browsing context. Under normal circumstances, this is reasonable, but it requires very tight synchronization between script, layout, the constellation and the compositor. In particular, if a layout is in progress when an iframe's browsing context is discarded, this can trigger panic.
This PR fixes this in two ways:
1. Making the pipeline and browsing context ids optional in layout's representation of an iframe.
2. Shutting down layout before discarding a browsing context, rather than after.
This is belt and braces.
---
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- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix#17482 and #18477
- [X] These changes do not require tests because the PR is fixing a panic caused by a race condition
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Using OnceCell<T> from Mitochondria
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#13402 (github issue number if applicable).
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