Remove old-style processing-instruction based syntax from DOM Parts
This has been replaced (in a few long-past CLs) with the newer
brace-based syntax, e.g. <div {{}}>.
Bug: 40271855
Change-Id: I38fb6338170c721585ea71c635066f12d39f81e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5605653
Commit-Queue: David Baron dbaron@chromium.org
Reviewed-by: Joey Arhar jarhar@chromium.org
Auto-Submit: Mason Freed masonf@chromium.org
Reviewed-by: David Baron dbaron@chromium.org
Cr-Commit-Position: refs/heads/main@{#1312573}