It could be used to have mutable JSVal fields without GC barriers.
With the removal of that trait, MutHeap and MutNullableHeap can respectively
be replaced by MutJS and MutNullableJS.
The purpose of the code changes is to enable the use of promises in the Service Worker container. I also modified the Service Worker test in order to support the promises.
Implement postMessage for ServiceWorkers
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Fixes#12773
r? @jdm
Changes:
* Implements `postMessage` on `ServiceWorker` object.
* Removes unused channels from sw and their scopes.
* Fixes a crash when calling `scope.script_chan()` in sw-scopes event handling.
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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#12773
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- [X] There are tests for these changes at `tests/html/service-worker`
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Consistently use the name 'pipeline_id' to refer to a function that
returns an (optional) PipelineId.
This was prompted by discovering both fn pipeline and fn pipeline_id
doing the same job in htmliframeelement.rs.
Note that there is fn pipeline in components/compositing/compositor.rs,
but that actually returns an Option<&CompositionPipeline>, not any kind
of PipelineId.
