Refactor corner shape path drawing

Instead of passing the corner rect to the function and using a
switch/case, pass 4 points, ordered clockwise, which represent the
corner rect. This removes a lot of redundant logic.

Bug: 394059604

R=fs@opera.com

Change-Id: I33eb809148e271f895b60238cb227f1750cca572
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6351925
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Noam Rosenthal <nrosenthal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1432928}