Andreas Kling 194f17928f LibWeb: Cache parsed selectors for querySelectorAll/querySelector ...

Add a per-Document cache that maps selector strings to their parsed
SelectorList results. This avoids re-tokenizing and re-parsing the
same selector strings on every call, which is a huge win for pages
that repeatedly call querySelectorAll with the same selectors.

On microsoft.com, where they spam querySelectorAll with the same two
selectors, profiling showed 62% of main thread time was spent
re-parsing selectors. This cache eliminates that entirely for
repeated queries.

2026-03-20 18:32:32 -05:00

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