Revert "Use base::HeapArray in image_writer"

This reverts commit d63d4f17.

Reason for revert: Image writing broken on macOS: crbug.com/332755373

Original change's description:
> Use base::HeapArray in image_writer
>
> Fixed: 326458515
> Fixed: 326458575
> Fixed: 326458512
> Fixed: 326458573
> Fixed: 326458647
> Fixed: 326457992
> Fixed: 326458493
> Change-Id: I7470fd577ae42b983bd6ba1c858c645452e4f9d2
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5398380


> Auto-Submit: Avi Drissman <avi@chromium.org>
> Commit-Queue: Reilly Grant <reillyg@chromium.org>
> Reviewed-by: Reilly Grant <reillyg@chromium.org>
> Commit-Queue: Avi Drissman <avi@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1279140}

Bug: 332755373
Change-Id: I7f82bbc5533dcc6aa44140541bbf9407daa3bc01
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5427823


Auto-Submit: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1283344}