Move scrollbar and border adjusting logic inside GetScrollOffsetToExpose
Also, while moving this logic inside GetScrollOffsetToExpose,
fix the bug for RootFrameViewport not having this logic before.
Bug: 355460994
Change-Id: I3923ebfe262da0992fbbf68a23fcccee70985b86
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5741211
Commit-Queue: Daniil Sakhapov sakhapov@chromium.org
Reviewed-by: David Bokan bokan@chromium.org
Cr-Commit-Position: refs/heads/main@{#1342299}