I added a failure expectation because we still need to figure out if the
anchor element should work in XML documents or not, but this patch still
fixes a crash when the anchor attribute is set in XML.

If we decide that the anchor attribute shouldn't work in XML, then I'll
have to move the IDL and some methods from Element to HTMLElement which
will be a bigger patch.

Fixed: 334368377
Change-Id: Id3a016a838a5ce5b3adac445b7bcf7be4bbc3160
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5455394
Reviewed-by: Joey Arhar <jarhar@chromium.org>
Commit-Queue: Prudhvikumar Bommana <pbommana@google.com>
Cr-Commit-Position: refs/branch-heads/6420@{#7}
Cr-Branched-From: df576e0dad8b00dea2749a08f0849c518fa28949-refs/heads/main@{#1287100}