ServoStyleSetSizes now has two uses, one for the Stylist, and one for the UA
cache, and so the patch removes 'Stylist' from the field names.
Example output from about:memory:
> +----1,359,608 B (00.55%) -- layout
> | +----756,488 B (00.31%) -- style-sheet-cache [2]
> | +----393,968 B (00.16%) -- servo-ua-cache
> | | +--234,496 B (00.10%) -- element-and-pseudos-maps
> | | +---59,648 B (00.02%) -- revalidation-selectors
> | | +---58,320 B (00.02%) -- invalidation-map
> | | +---30,752 B (00.01%) -- other
> | | +---10,752 B (00.00%) -- precomputed-pseudos
Share specified URLs with Gecko
This makes use of our Arc offset machinery to allow Gecko to store Arc<String> values and ensure there are used appropriately.
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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 [bug 1397971](https://bugzilla.mozilla.org/show_bug.cgi?id=1397971).
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Measure memory usage of Stylo's Rule Tree.
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This is for https://bugzilla.mozilla.org/show_bug.cgi?id=1394729, which was r=heycam.
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The patch provides FFI access to Gecko's SeenPtrs type from Rust, in
order to record what has already been measured when measuring Arcs. (The
SeenPtrs must be initialized on the Gecko side because the same table is
reused for measuring all Elements within a window, because Elements can
share ComputedValues.) I have confirmed with DMD that this is working
correctly.
The patch also introduces MallocSizeOfRepeats, which is like
MallocSizeOf but takes a SizeOfState, which holds a SeenPtrs table.
