1888082 - Consider to share string data from JS to DOM

Status: NEW

(Core :: DOM: Bindings (WebIDL), enhancement, P3)

Description

[Olli Pettay [:smaug][[e-mail]]]

Right now strings are often copied.
peterv's wip patch shows some improvements https://treeherder.mozilla.org/perfherder/comparesubtest?originalProject=try&newProject=try&newRevision=b9f7d5f3fab966751bd8829c0a20ead47fe4208a&originalSignature=4586009&newSignature=4586009&framework=13&application=firefox&originalRevision=86dae3ae5a98e6155f363a0fc756ab0e8e045243&page=1&replicates=1&showOnlyConfident=1
(and since those results may disappear eventually, they seem to hint about ~0.5% in several sp3 subtest)

One thing to figure out is how to ensure JS string data doesn't move.