We received a report on webcompat.com which boiled down to site navigation being partly broken because document.querySelector("::-webkit-scrollbar") throws an error: >SyntaxError: '::-webkit-scrollbar' is not a valid selector In this case, it was throwing in a commercial web library by 3D Issue, so it's likely that other sites are also going to have problems with this (given that this is a pseudo-element that works in Chrome/WebKit). Perhaps we ought to not throw in this case, but simply return no elements for that pseudo-element?
I'd be hesitant to do this based on a single report, since this is a mechanism that can be used to tell whether a selector is actually supported.
Webcompat Priority: --- → ?
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