Reland: FaceGaze: adjust bubble location

This is a reland of https://crrev.com/c/5878003. The original CL was
reverted because of crashes on asan/lsan builds. The fix is to create a
copy of the work area rect, instead of using a const reference.

Original change description:

This change updates the location of the FaceGaze bubble UI so that it
considers other UI elements such as the ChromeVox panel. We also account
for the fact that the work area may not start at (0, 0).

See this screenshot, which shows the location of the bubble (it
displays "hello world" in the screenshot).

https://drive.google.com/file/d/1fl07we-oua9zqyQSa_T5ZsmCOUdWWL5T/view?usp=sharing&resourcekey=0-t20E0amGVhTQ_RT9C--h3g

Bug: 367774352
Change-Id: Ia0054ab980081cbc75139a4ae44425c1a49d0179
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5886851
Commit-Queue: Akihiro Ota <akihiroota@chromium.org>
Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1359594}