merge_pr_46415

[anchor] Fix anchor-center crash.

We had a NOTREACHED within grid for anchor-center when it was valid.
Ensure it maps to center.

Bug: 341928664
Change-Id: If9fa88f9febb31333d3d646dfce356cc1456259e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5552987
Commit-Queue: Mason Freed masonf@chromium.org
Reviewed-by: Mason Freed masonf@chromium.org
Auto-Submit: Ian Kilpatrick ikilpatrick@chromium.org
Cr-Commit-Position: refs/heads/main@{#1304494}