chore: cherry-pick 9b3d0e2f1aab from chromium

[ppontes]

Keep a reference to the transfer buffer in Dawn read/write handles.

Previously the Dawn read/write handles in the GPU process only contained
a pointer to the inside of a shmem region owned by a gpu::Buffer that
had a different lifetime. This could allow a renderer process to
deallocate the memory from underneath the handle which is bad.

Fix this by keepind a scoped_refptr to the gpu::Buffer inside the
read/write handles to extend the lifetime of the shmem to be at least as
big as the handle's.

Fixed: chromium:1393177
Change-Id: I9d9c18d5155a46e0e3a01d385d221a6370bd2bea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4056276
Reviewed-by: Austin Eng enga@chromium.org
Commit-Queue: Corentin Wallez cwallez@chromium.org
Cr-Commit-Position: refs/heads/main@{#1076828}

Notes: Security: backported fix for 1393177.

[release-clerk]

Release Notes Persisted

Security: backported fix for 1393177.