sideways: Support scroll anchoring
- Store the anchor object offset as a LogicalOffset, not a block-
flipped LayoutPoint - Add functions converting between LogicalOffset and gfx::Vector2d /
gfx::PointF / ScrollOffset.
Bug: 40501131
Change-Id: I8d32b1a2a8e9fc6ade68f12188430ac768dd14d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5933384
Reviewed-by: Koji Ishii kojii@chromium.org
Auto-Submit: Kent Tamura tkent@chromium.org
Commit-Queue: Koji Ishii kojii@chromium.org
Cr-Commit-Position: refs/heads/main@{#1369217}