After bug 2025271 we support unowned buffers, so we can do this, which optimizes some conversions like the ones described in bug 1854446: https://searchfox.org/firefox-main/rev/7b74d86ca4ce65e82fdaa3095d2d39a26d3ac4f6/dom/base/CustomElementRegistry.cpp#274-276 Arguably those probably hit the inline string cache now, but still seems like a common enough thing to do. Differential Revision: https://phabricator.services.mozilla.com/D289180