Move backdrop-filter blur tests to wpt using fuzzy matching filter refs
This moves the backdrop-filter blur tests over to wpt, adding a
javascript helper function to simulate the expected edge mirror
backdrop blur with a normal blur filter.
Bug: 40040614
Change-Id: Icc18663934f88e9d24989f862fcbe8e087587401
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5663866
Commit-Queue: Robert Flack flackr@chromium.org
Reviewed-by: Chris Harrelson chrishtr@chromium.org
Cr-Commit-Position: refs/heads/main@{#1322361}