…Resizing crash

This clamps the values of `GetClosestFixedDividerPosition()` and
`CalculateDividerPosition()` to be between 0 and the work area length.

Test: compiles
Bug: b/327685487
Change-Id: Ifba1dad1b79208292094844eb2a6ab86941dc637
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5414873
Commit-Queue: Sophie Wen <sophiewen@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1282845}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5449870
Cr-Commit-Position: refs/branch-heads/6367@{#798}
Cr-Branched-From: d158c6dc6e3604e6f899041972edf26087a49740-refs/heads/main@{#1274542}