[Sanitizer] Implement core Sanitizer data structures + logic.
This implements the core Sanitizer logic. This is still missing
spec-mandated handling of "javascript:" URLs, and will have to be
updated as the spec develops. But other than that, the basics are now
there.
Bug: 356601280
Change-Id: I1de1da05b80d54e8082fc094d8a857f1c2284ac0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5922125
Commit-Queue: Daniel Vogelheim vogelheim@chromium.org
Reviewed-by: Joey Arhar jarhar@chromium.org
Cr-Commit-Position: refs/heads/main@{#1382913}